ASSESSMENT OF APPLICATION OF GPR ON DIFFERENT TYPES OF SOIL SURROUNDING SULAIMANI CITY, IRAQI KURDISTAN REGION A thesis Submitted to the Council of Faculty of Science and Science Education, School of Science, University of Sulaimani in Partial Fulfillment of the Requirements for the Degree of Master of Science in Geology
By HALO ABDULLAH OTHMAN B.Sc. Geology (2006), University of Sulaimani Supervised by Dr. Bakhtiar Qader Aziz Professor
2014 A.D.
2714 Kurdish
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Dedication To:
my parents, brothers and my sister
my teachers in all stages of my study
my friends
those who helped me in this research
the geologists especially Geophysicists
all teachers in the Geology Department
Geology department
my country, Kurdistan and all Kurdish citizen
those who discover new topics in Geology
those who like science
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Acknowledgments Thanks to Allah who supported me to carry out this research as well as my course studies. I am very grateful to my sincere supervisor Prof. Dr. Bakhtiar Qader Aziz for his recommendation in selecting the research proposal and his sincere help in fulfilling the research as well as his encouragement during the course of the study. Sincere thanks to Dr. Peshawa M. Ali who helped me in repairing the GPR device. My special word of thanks would go to my lovely father who helped me in the fieldwork. Great thanks to the Iraqi Geological Survey Affairs and its agency in Sulaimani city for analyzing the samples by XRD. Great thanks to Chemistry Department especially Mr. Dler Mohammad for his tremendous help in analyzing the samples by ICP device. Special thanks to Agriculture Department, Soil and Water department for their assistant in analyzing the soil samples. I would also like to extend my gratitude and thanks to the head of Geology Department for their stimulating support in providing the GPR system. Great thanks to the Mala Geoscience office, Sweden, for their help to repair the GPR device. The agency of the Mala Geoscience in Baghdad also helped me in repairing the GPR device. Finally, Iam very grateful to those who assisted me in all the stages of my research.
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Abstract Ground Penetrating Radar for soil suitability is investigated in different sites around Sulaimani, Iraqi Kurdistan Region. The sites are bounded by Northing point of (3929740.00 N, 3947902.00 N) and Easting point of (542059.00 E, 530496.00 E) and tectonically located in the low folded zone, high folded zone and imbricated zone. The current study includes the effect of soil thickness, soil moisture and soil composition that is clay and non-clay minerals, salinity and soil texture on the strength of radar signals. Seven sites are selected around Sulaimani, located on different soils due to different geological formation such as Pilaspi, Tanjero, Lower Fars, Kometan, Redbed Series, Shiranish and U.Fars Formations. The Ground Penetrating Radar/Mala Ramac is used to data acquisition and using of 100 MHZ antenna. Three traverses of 50 m length are plotted in each location and on different soil thickness from different horizontal distances of the outcrops. The measurements were carried out by using the same setting of the parameters for all the studied locations such as Frequency antenna, Time window, Trig interval, Number of samples and sample frequency. The radar sections recorded and processed by using the suitable filters and converting them from the time domain to the depth section. The first traverse in each location was carried out on 4 m soil thickness, second is on 8 m and third is on 12 m soil calculated by a special design in the field with support of the other data such as dip angle of the beds. The surveys were carried out in two different seasons, April and October of 2013 having different moisture conditions in determining the effect of soil moisture on the radar signals and depth of the penetration. The soil samples were collected at each site and were analyzed to minerals content, salinity and soil texture for the determination of their effect on the radar signals. The soil thickness effects on the radar signals were calculated, showing that the depth of penetration is decreased by 1.2 % for each meter of the soil, and the signal amplitude is decreased by 6.1 % for each meter of the soil. The soil moisture effect on the radar signals is also studied and as a result the depth of penetration, from the dry to the wet condition, is decreased by 11.06 %, and the radar signal amplitudes from the dry to the wet condition are decreased by 56.2 %. The soil composition effects on the radar signals are studied, they are mineralogical composition of the soil, chemical composition of the soil and the soil texture. The soils are analyzed mineralogically, maximum amplitude attenuation was observed in high percent of III
Montmorillonite and Calcite and minimum amplitude attenuation was recoded in high percentage of kaolinite, Gypsum, Quartz and Illite as in the location two. The soil samples are analyzed chemically for calculating the ratio of abundant elements such as Ca, Mg, K and Na, generally the maximum amplitude attenuation observed in the high concentration ratio of the Ca, Mg, Na and sodium absorption ratio or soil sodicity. The soil samples are also analyzed for their texture of sand, silt and clay effects on the radar signals. It was concluded that the maximum amplitude attenuation in the whole studied samples is recorded in high percentage of silt and clay and low attenuation in the low silt, clay and high sand particles content. The studied soils that are located on the different geological formations showed that the soils on the Lower Fars, Kometan and Tanjero Formations are more suitable for the GPR survey than soils located on other geology formations. A map of the soil suitability for GPR is created around Sulaimani.
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List of Contents Dedication ............................................................................................................................... I Acknowledgment ................................................................................................................ II Abstract ..............................................................................................................................III
Chapter One: Introduction 1.1 Preface .......................................................................................................................... 1 1.2 Locations of the Study Area ......................................................................................... 1 1.3 Geology and Stratigraphy............................................................................................. 3 1.4 Tectonic Setting............................................................................................................ 6 1.5 Literature Review ....................................................................................................... 11 1.6 The Aim of the Study ................................................................................................. 12
Chapter Two: A Theoretical Background 2.1 Preface ........................................................................................................................ 13 2.2 Basic Principles of the GPR ....................................................................................... 13 2.3 GPR Field Systems..................................................................................................... 14 2.4 GPR Signal and Soil Composition ............................................................................. 16 2.5 Instrumentation........................................................................................................... 18 2.6 Data Processing and Interpretation ............................................................................ 19 2.7 Velocity Analysis ....................................................................................................... 21 2.8 Methodology .............................................................................................................. 23
Chapter Three: Data Collection and Processing 3.1 Preface ........................................................................................................................ 24 3.2 Data Collection........................................................................................................... 24 3.3 Data Processing .......................................................................................................... 25 3.4 Survey Design ............................................................................................................ 29
Chapter Four: The Effect of Soil Thickness on Radar Signals 4.1 Preface ........................................................................................................................ 34 4.2 Analysis of Soil Thickness Effect .............................................................................. 34 V
4.3 Amplitude Analysis.................................................................................................... 47 4.4 Spectra Analysis ......................................................................................................... 63
Chapter Five: The Effect of Soil Moisture on Radar Signals 5.1 Preface ........................................................................................................................ 72 5.2 Soil Moisture Effect on the Depth of Penetration ...................................................... 73 5.3 Amplitude Analysis.................................................................................................... 80 5.4 Spectra Analysis ......................................................................................................... 92
Chapter Six: The Effect of Soil Composition on Radar Signals 6.1 Preface ........................................................................................................................ 99 6.2 Calculated Parameters .............................................................................................. 100 6.2.1 Effect of the Minerals on Radar Signals ............................................................... 100 6.2.2 Chemical Composition Effect on the Radar Signals ............................................. 106 6.2.3 Soil Texture Effect on the Radar Signals .............................................................. 111 6.3 Soil Attributes and Index Value ............................................................................... 116
Chapter Seven: Results, Conclusions and Recommendations 7.1 Conclusions .............................................................................................................. 120 7.2 Recommendations .................................................................................................... 121 7.3 References ................................................................................................................ 122
List of figures 1.1 Locations of the study area (Google map) ................................................................... 3 1.2 GPR traverses at location 1 .......................................................................................... 6 1.3 GPR traverses at location 2 .......................................................................................... 7 1.4 GPR traverses at location 3 .......................................................................................... 7 1.5 GPR traverses at location 4 .......................................................................................... 8 1.6 GPR traverses at location 5 .......................................................................................... 8 1.7 GPR traverses at location 6 .......................................................................................... 9 1.8 GPR traverses at location 7 .......................................................................................... 9 1.9 Studied locations on the geology map (Jassim and Goff, 2006) ................................ 10 VI
1.10 Locations on the tectonic map of Iraq (After Jassim and Goff, 2006) ........................ 10 2.1 Diagram showing of the parts of the GPR system (Jol, 2009) ................................... 14 2.2 Showing two types of GPR survey in the field (Bristow and Jol, 2003) ................... 15 2.3 Shows GPR field work in fixed mode at location 1 .................................................. 16 2.4 Depth of penetration in different geological materials(Google search) ..................... 18 2.5 Shows different parts of the GPR device ................................................................... 19 2.6 GPR data processing flow chart (Jol, 2009)............................................................... 21 2.7 Shows common mid-point analysis (CMD)............................................................... 22 3.1 Shows the main window of the ground vision software 1.4.2 ................................... 25 3.2 Shows the main window of the Rad. explorer, version1.41....................................... 27 3.3 Modeling of the radar sections ................................................................................... 29 3.4 The Soil thickness calculation model in the field ...................................................... 30 3.5 3D sketch of the field work at the location 1 ............................................................. 31 4.1 Shows a large soil thickness in the Bazian area ......................................................... 34 4.2 Radar section at location 1, traverse one (100MHZ) ................................................. 35 4.3 Radar section at location 1, traverse two (100MHZ) ................................................. 36 4.4 Radar section at location 1, traverse three (100MHZ) ............................................... 36 4.5 Radar section at location 2, traverse one (100MHZ) ................................................. 37 4.6 Radar section at location 2, traverse two (100MHZ) ................................................. 38 4.7 Radar section at location 2, traverse three (100MHZ) ............................................... 38 4.8 Radar section at location 3, traverse one (100MHZ) ................................................. 39 4.9 Radar section at location 3, traverse two (100MHZ) ................................................. 40 4.10 Radar section at location 3, traverse three (100MHZ) ............................................. 40 4.11 Radar section at location 4, traverse one (100MHZ) ............................................... 41 4.12 Radar section at location 4, traverse two (100MHZ) ............................................... 42 4.13 Radar section at location 4, traverse three (100MHZ) ............................................. 42 4.14 Radar section at location 5, traverse one (100MHZ) ............................................... 43 4.15 Radar section at location 5, traverse two (100MHZ) ............................................... 44 4.16 Radar section at location 5, traverse three (100MHZ) ............................................. 44 4.17 Radar section at location 6, traverse one (100MHZ) ............................................... 45 4.18 Radar section at location 6, traverse two (100MHZ) ............................................... 46 4.19 Radar section at location 6, traverse three (100MHZ) ............................................. 46 4.20 Amplitude in traverse 1, 2 and 3 of different depth at location 1 ............................ 49 VII
4.21 Amplitude in traverse 1, 2 and 3 of different depth at location 2 ............................ 51 4.22 Amplitude in traverse 1, 2 and 3 of different depth at location 3 ............................ 53 4.23 Amplitude in traverse 1, 2 and 3 of different depth at location 4 ............................ 55 4.24 Amplitude in traverse 1, 2 and 3 of different depth at location 5 ............................ 57 4.25 Amplitude in traverse 1, 2 and 3 of different depth at location 6 ............................ 59 4.26 Amplitude in traverse 1, 2 and 3 of different depth at location 7 ............................ 61 4.27 Spectra analysis at location 1 ................................................................................... 64 4.28 Spectra analysis at location 2 ................................................................................... 65 4.29 Spectra analysis at location 3 ................................................................................... 66 4.30 Spectra analysis at location 4 ................................................................................... 77 4.31 Spectra analysis at location 5 ................................................................................... 68 4.32 Spectra analysis at location 6 ................................................................................... 69 4.33 Spectra analysis at location 7 ................................................................................... 70 5.1 Shows dry and wet condition of survey at the same place at location 1 .................... 72 5.2 Radar section at location one, traverse two, wet condition (100MHZ) ..................... 74 5.3 Radar section at location two, traverse two, wet condition (100MHZ) .................... 74 5.4 Radar section at location three, traverse two, wet condition (100MHZ) ................... 76 5.5 Radar section at location four, traverse two, wet condition (100MHZ) .................... 76 5.6 Radar section at location five, traverse two, wet condition (100MHZ) ..................... 77 5.7 Radar section at location six, traverse two, wet condition (100MHZ) ...................... 78 5.8 Shows depth of penetration in dry and wet conditions .............................................. 79 5.9 Amplitude in dry and wet condition of different depth at location 1 ......................... 80 5.10 Amplitude in dry and wet condition of different depth at location 2 ....................... 83 5.11 Amplitude in dry and wet condition of different depth at location 3 ....................... 85 5.12 Amplitude in dry and wet condition of different depth at location 4 ....................... 87 5.13 Amplitude in dry and wet condition of different depth at location 5 ....................... 89 5.14 Amplitude in dry and wet condition of different depth at location 6 ....................... 91 5.15 Spectra analysis in dry and wet condition at location 1 ........................................... 92 5.16 Spectra analysis in dry and wet condition at location 2 ........................................... 93 5.17 Spectra analysis in dry and wet condition at location 3 ........................................... 94 5.18 Spectra analysis in dry and wet condition at location 4 ........................................... 95 5.19 Spectra analysis in dry and wet condition at location 5 ........................................... 96 5.20 Spectra analysis in dry and wet condition at location 6 ........................................... 97 VIII
6.1 Showing a sample of the soil components (Google search) ..................................... 100 6.2 Shows minerals percentage at the studied locations ............................................... 103 6.3 Chemical composition of the soil samples .............................................................. 108 6.4 Showing the sand, silt and clay % in the soils at studied locations ......................... 113 6.5 The ground penetrating radar soil suitability map around Sulaimani .................... 119
List of tables 3.1 Shows a set of parameters used in the data collection ............................................... 25 3.2 Shows attenuation and relative permittivity of the soils (Daniels, 2004) .................. 37 3.3 Shows attenuation and relative permittivity of the materials (Daniels, 2004) ........... 38 3.4 Collected data from the field work............................................................................. 32 3.5 Parent rock, Formations and place of the GPR survey .............................................. 33 4.1 Soil thickness and depth of penetration at location 1 (100MHZ) .............................. 35 4.2 Soil thickness and depth of penetration at location 2 (100MHZ) .............................. 37 4.3 Soil thickness and depth of penetration at location 3 (100MHZ) .............................. 39 4.4 Soil thickness and depth of penetration at location 4 (100MHZ) .............................. 41 4.5 Soil thickness and depth of penetration at location 5 (100MHZ) .............................. 43 4.6 Soil thickness and depth of penetration at location 6 (100MHZ) .............................. 45 4.7 Amplitude in traverse 1, 2 and 3 at location 1 .......................................................... 48 4.8 Amplitude in traverse 1, 2 and 3 at location 2 .......................................................... 50 4.9 Amplitude in traverse 1, 2 and 3 at location 3 .......................................................... 52 4.10 Amplitude in traverse 1, 2 and 3 at location 4 ........................................................ 54 4.11 Amplitude in traverse 1, 2 and 3 at location 5 ......................................................... 56 4.12 Amplitude in traverse 1, 2 and 3 at location 6 ........................................................ 58 4.13 Amplitude in traverse 1, 2 and 3 at location 7 ......................................................... 60 4.14 Showing of the amplitude decreasing percentage after increasing of 8 m soil ...... 62 4.15 Maximum and minimum amplitude % in the spectra analysis ............................... 71 4.16 Difference in the maximum amplitude between the first and third traverse ........... 71 5.1 Depth of penetration in dry and wet conditions ........................................................ 79 5.2 Amplitude in dry and wet condition at location 1 ..................................................... 81 5.3 Amplitude in dry and wet condition at location 2 ..................................................... 82 5.4 Amplitude in dry and wet condition at location 3 ..................................................... 84 5.5 Amplitude in dry and wet condition at location 4 ..................................................... 86 IX
5.6 Amplitude in dry and wet condition at location 5 ..................................................... 88 5.7 Amplitude in dry and wet condition at location 6 ..................................................... 90 5.8 Maximum amplitude in dry and wet condition and their difference ......................... 98 6.1 Shows mineral composition and Ground Penetrating Radar ................................. 105 6.2 Shows element concentrations, SAR, Depth, Max.amplitude and attenuation ...... 110 6.3 Shows Textural classification of soils and Ground Pene trating Radar data. .......... 115 6.4 Index value, GPR suitability and attribute index value .......................................... 116 6.5 Index value of the soil parameters ........................................................................... 117 6.6 Soil attributes for Ground penetrating radar suitability ............................................ 118
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Chapter One Introduction
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Chapter One
Introduction
1.1 Preface Increasingly, Ground Penetrating Radar (GPR) is used in agronomic, archaeological, engineering, environmental, hydrogeology, cavities and soil investigations. Current news articles report the use of GPR in crime scene investigations and detection of terrorism and military hazards (Doolittle et al, 2007). However, a thin, conductive soil horizon or layer causes high rates of signal attenuation, severely restricting penetration depths and limiting the suitability of GPR for a large number of applications. In saline and sodic soils, where penetration depth are typically less than 25 cm (Daniels, 2004), GPR is an inappropriate tool. In wet clays, where penetration depths are typically less than 1 m (Doolittle et al, 2007), GPR has a very low potential for many applications. Most GPR users have limited knowledge of soils and are unable to foretell the relative suitability of soils for GPR within project areas. In this research a group of parameters that have great effect on radar signals were studied in several locations surrounding Sulaimani. These parameters are wet and dry conditions of soil, different thickness of soil as well as mineral and chemical composition of soil. In each location, the survey was carried out by using of 100MHZ antenna.
1.2 Locations of the Study Area The whole selected sites for the study are located around Sulaimani, Kurdistan Region, NE Iraq. These sites are located on different geological formations such as Pilaspi, U.Fars, Tanjero, Kometan, Redbed Series, Shiranish and L. Fars Formation. They are the parent rock for the soils that are located on them, as shown in figure 1.1.
1.2.1 Location 1 It is located near Gopala, a Village about 36 km W of Sulaimani. The location is situated at the intersection point of (503024.60 E, 3943111.00 N). It is located on Pilaspi Formation.
1.2.2 Location 2 It is located near west of Takya, a town about 48.2 km W of Sulaimani. The location is situated at the intersection point of (492273.00 E, 3947902.00 N). It is located on Lower Fars Formation.
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Introduction
1.2.3 Location 3 It is located near Kani Bardina, a village about 9.8 km north of Sulaimani. The location is situated at the intersection point of (536298.00 E, 3943562.00 N). It is located on Shiranish Formation.
1.2.4 Location 4 It is located near the Darbarula, a village about 10.7 km SE of Sulaimani. The location is situated at the intersection point of (547158.00 E, 3928125.00 N). It is located on Kometan Formation.
1.2.5 Location 5 It is located near Azaban, a village about 12.1 km NE of Sulaimani. The location is situated at the intersection point of (549413.00 E, 3939971.00 N). It is located on Tanjero Formation.
1.2.6 Location 6 It is located near the Sura Qalat, a village about 24 km N of Sulaimani. The location is situated at the intersection point of (542059.00 E, 3958165.00 N). It is located on Red Bed Series.
1.2.7 Location 7 It is located near the Qaradagh, a town about 30 km SW of Sulaimani. The location is situated at the intersection point of (530496.00 E, 3905832.00 N). It is located on U. Fars Formation.
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Figure 1.1: Locations of the study area (Google map)
1.3 Geology and Stratigraphy The studied sites are selected because they are located on different geological formations, as shown in figure 1.9. Consequently, physical properties, mineral and chemical compositions of the soil covers of these formations are various. What follows is a description of the geological formations of each location.
1.3.1 Location 1 It is located on Pilaspi Formation, the upper part of the formation comprises well bedded, bituminous, chalky, and crystalline limestone, with bands of white, chalky marl and with chert nodules toward the top. The lower part comprises well bedded, hard porous or vitreous, bituminous, white, poorly fossiliferous limestones, with algal or shell sections. It has Thickness ranging from 100-200 m (Jassim and Goff, 2006). The soil covers are calcareous and rich with rock fragments of different size of limestone rock that has a great 3
Chapter One
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thickness of about 0-150m (Aziz, 2005) in current area, as shown in figure 1.2.
1.3.2. Location 2 It is located on the Lower Fars Formation, its type section has been established in Iraq in the al Fatha gorge. So it was named Al Fatha Formation, it comprises anhydrite, gypsum and salt interbedded with limestone and marl (Jassim and Goff, 2006). The soil cover is rich with various types of gypsum, limestone, sandistone and marl rock fragments. The thickness of soil in this location is less than in location 1, figure 1.3.
1.3.3 Location 3 It is located on the Shiranish Formation. In its type area comprises thin bedded argillaceous limestone (locally dolomitic) overlain by blue pelagic marls. Limestone conglomerates occur locally in the formation. The formation gradually passes into Tanjero Formation to the NE. In the type area, it is 225 m thick, in other outcrop areas it varies in thickness from 100 to 400 m. In the type section, the Shiranish Formation conformably overlies the Bekhma Formation (Jassim and Goff, 2006). The soil contains high rate of calcium carbonate derived from the limestone rocks of Shiranish Formation. The soil thickness is less than in location 1 and 2, as shown in figure 1.4.
1.3.4 Location 4 It is located on the Kometan Formation. The formation comprises 120 m of light grey, thin bedded, Globigerinal-Oligosteginal limestone locally silicified with chert concretions in some beds, with glauconitic bed at the base. Sediments of the Kometan Formation were deposited in different environments ranging from shallow shelfs, restricted to open marine (Jassim and Goff, 2006). The soil is highly mixed with different sizes of limestone rock fragments that give a calcareous property to the soil, as shown in figure 1.5.
1.3.5 Location 5 It is located on Tanjero Formation. It comprises two divisions: the lower division comprises pelagic marl, and occasional beds of argillaceous limestone with siltstone beds in the upper part. The upper division comprises silty marl, sandstone, conglomerates and 4
Chapter One
Introduction
sandy or silty organic detrital limestone. It interfingers with Aqra limestone Formation. The sandstones are composed of predominantly grains of chert and green igneous and metamorphic rocks. Conglomerates contain pebbles of Mesozoic limestone, dolomites, recrystallized limestone, and radiolarian chert. The thickness of the formation is very variable, the maximum thickness of the formation is about 2000 m (Jassim and Goff, 2006). Soils of this area are highly affected by the different component of the formation, as shown in figure 1.6.
1.3.6 Location 6 It is located on the Red Bed Series, the series divided into the lower Suwais Redbed, the middle Lailuk limestone and upper Merga Red bed. It was deposited into two basins on either side of the lower Masttrichtian thrust belt. The Suwais I Red beds unit comprises lenticular fossiliferous, detrital and massive conglomeratic limestone beds with red ferruginous shales in the upper part. The Suwais II unit consists of flysh with rhythmically interbedded dark red ferruginous siliceous silty shales and blue grey siltstones these sediments contain locally beds and lenticular bodies of conglomerate and very fossiliferous limestones. The Suwais III unit consists of coarse partly block sized conglomerates with abundant chert boulders derived from the Qulqula Radiolarian Formation. Numerous boulders of volcanic and sedimentary rocks of unknown derivation also occur. The Suwais IV unit in the type area comprises red calcareous shales and sandstones with layers of reddish or grey Nummulitic limestone and conglomerates (Jassim and Goff, 2006). Soils of this area are affected by lithological components of the Red Bed Series, as shown in figure 1.7.
1.3.7 Location 7 It is located on the U. Fars Formation, the basal unit comprises thin bedded calcareous sandstones, red and green mudstones with one thin gypsum bed and a purple siltstone with glass shards (Jassim and Goff, 2006). In the type area its thickness is about 620 m. Soils that located on it contains a great amount of grains that derived from the U. Fars Formation. The soil thickness is less than in location 1 and 2, as shown in figure 1.8.
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Introduction
1.4 Tectonic Setting Tectonically the studied area is complex and is located in the unstable part of the Arabian plate. It is sub ducted to the Iranian plate, for that Iraq divided tectonically in to Suture zone, unstable shelf and Stable shelf. The Unstable shelf in Iraq is divided in to four zones: the Foothill zone, the High folded zone, and the Imbricated Northern (Ora) and Balambo-Tanjero zone. The Unstable shelf has been the most strongly subsiding part of the Arabian plate since the opening of the southern Neo-Tethys in the late Jurassic. Maximum subsidence occurred during the late Cretaceous Ophiolite obduction on to the NE margin of the Arabian plate and during Mio-Pliocene continental collision. The unstable shelf is thus characterized by the structural trends and facies changes that are parallel to the ZagrosTaurus suture belts. Surface folds are characteristic feature of the unit (Jassim and Goff, 2006). Locations 1, 3, 4, and 7 are located in the high folded zone while location 2 is located in the Foothill zone, and location 5 and 6 are located in the Imbricated zone, as shown in figure 1.10.
Figure 1.2: GPR traverses at location 1 6
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Introduction
Figure 1.3: GPR traverses at location 2
Figure 1.4: GPR traverses at location 3 7
Chapter One
Introduction
Figure 1.5: GPR traverses at location 4
Figure 1.6: GPR traverses at location 5 8
Chapter One
Introduction
Figure 1.7: GPR traverses at location 6
Figure 1.8: GPR traverses at location 7 9
Chapter One
Introduction
Figure 1.9: Studied locations on the Geology map (Jassim and Goff, 2006)
Figure 1.10: Locations on the tectonic map of Iraq (After Jassim and Goff, 2006) 10
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Introduction
1.5 Literature Review There are several researches that have been carried out by using Ground Penetrating Radar in Kurdistan Region and in the world. Ground Penetrating Radar and Electrical Resistivity Studies for Hamamok Dam Site, NW Koya City, Kurdistan Region, Iraq: in which GPR was used for the subsurface study of the dam site, for the weak zones, cavities, water table and stratigraphic succession (Bakir, 2008). Hydrogeology and Geophysical investigation of Ganau Lake, Ranya area, Iraqi Kurdistan Region by Ali et al, 2011 is an approach adopted to characterize the basin configuration and
the possibility of vertical movements along the Jurassic rocks.
Furthermore, the influence of these variations could be mapped using Ground Penetrating Radar (GPR) in order to examine any subsidence in the area beneath the lake. The Geophysical investigation and Geological study of the Delga proposed Dam Site, Qala Diza, Sulaimani City, Kurdistan Region, NE-Iraq by Aziz et al, 2012. It aimed at evaluating the feasibility of the area for establishing dam foundation and reservoir. The GPR was used on the river terraces in the trough of the valley. The GPR survey showed that there are underground week zones (cavern and fractured zones) in restricted limited area. Karst cavity detection in carbonate rocks by integration of high resolution geophysical methods were carried out by Aziz and Ali, 2013. It is combined surveys using Ground Penetrating Radar (GPR) and Electrical Resistivity Tomography (ERT) for indicating characterization of the subsurface in karst environments. In the world, GPR research is carried out in several fields of investigation. Application of Ground Penetrating Radar in hydrogeologic studies was carried out by Milan and Haeni, 1991. In which the ground penetrating radar system was used to study used stratified drift deposits in Connecticut. Ground penetrating radar: antenna frequencies and maximum probable depths of penetration in Quaternary sediments were carried out by Smith and Jol, 1995. Ground penetrating radar (GPR) experiments were carried out in a gravel pit near Brigham, Utah, USA, to determine maximum probable depths of penetration for 25, 50, 100 and 200 MHz antennas. Spectral Analysis of Ground Penetrating Radar Response to Thin Sedimentary Layers: Ground penetrating radar (GPR) systems utilized in studies of sedimentary deposits gener11
Chapter One
Introduction
ate wavelengths (tens of centimeters) that are commonly much longer than the thickness of bedding (often millimeters to centimeters) within the target strata, by Guha et al, 2005. Ground Penetrating Radar soil suitability map of the conterminous United States (Doolittle et al, 2007), is a thematic map showing the relative suitability of soils for GPR applications within comparatively large areas of the United States. Attribute data used to determine the suitability of soils include taxonomic criteria, clay content, salinity, sodium absorption ratio, and calcium carbonate content. Dielectric permittivity of clay adsorbed water: Effect of salinity: study focuses on radar wave behavior through clays in close proximity with salt by (Aqil and Schmitt, 2010). The Use of Ground-Penetrating Radar to accurately estimate soil depth in Rocky forest Soils was carried out by Sucre et el, 2011. This study was conducted on three different physiographic regions across Appalachian mountains to estimate average soil depth. The influence of measurement conditions on depth range and resolution of GPR images, the example of lowland valley alluvial fill in Obra River, Poland, was carried out by Slowik, 2012. The Field experiment, based on the GPR surveys conducted at various groundwater levels and parameter settings, was carried out to study their influence on depth range and resolution of the GPR surveys.
1.6 The Aim of the Study is to: 1- Study the effect of soil thickness on the electromagnetic wave signals. 2-Evaluate the role of different mineral composition of the soil on the rate of the attenuation of radar signals. 3-Assessment radar signal penetration in both dry and wet conditions of soil. 4-Evaluate the role of chemical composition of the soil on the penetration of the radar signals. 5-Study the influence of different ratio of soil component (soil texture) on the reflection and penetration of radar signals.
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Chapter Two A Theoretical Background
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Chapter Two
A Theoretical Background
2.1 Preface Ground
Penetrating
Radar
(GPR) is a geophysical method
that employs an
electromagnetic technique (Reynolds, 1997). It is the general term applied to techniques which employ radio waves, typically in the 1 to 1000 MHz frequency range, to map structure and features buried in the ground (Annan, 2001). The method transmits and receives radio waves to probe the subsurface. Its use of radio waves to sound the earth was contemplated for decades before results were obtained in the 1950s (Bristow and Jol, 2003). The method has been extensively used in many applications, such as archaeology, civil engineering, forensics, geology and utilities detection (Daniels, 2004). Now GPR is equally well applied to a host of other media such as wood, concrete, and asphalt (Trevor et al, 2005). One of the earliest successful applications was measuring ice thickness on polar ice sheets in 1960s (Slowik, 2012). Since then, there have been rapid developments in hardware, measurement and analysis techniques. It is now a well-accepted geophysical technique. Waite’s demonstration of ice sheet sounding with aircraft radar altimeters leads to radio echo sounding in many locations around the world. From this start, there was a gradual transition of the concepts to sounding soils and rocks, which began in the 1960s, and has continued ever since. The method uses radio waves to probe the ground which means any low loss dielectric material. In its earliest inception, GPR was primarily applied to natural geologic materials.
2.2 Basic Principles of GPR A GPR system consists of a few components, as shown in Figure 2.1 that emit an electromagnetic wave into the ground and receive the response (Takahashi et al, 2012). If there is a change in electric properties in the ground or if there is an anomaly that has different electric properties than the surrounding media, a part of the electromagnetic wave is reflected back to the receiver with different depth of penetration. The system scans the ground to collect the data at various locations. Then a GPR profile can be constructed by plotting the amplitude of the received signals as a function of time and position, representing a vertical slice of the subsurface. The time axis can be converted to depth by assuming a velocity for the electromagnetic wave in the subsurface soil. The heart of the system is the timing unit which controls the generation of the radar signal and then the detection of receive signals as a function of time. 13
Chapter Two
A Theoretical Background
Figure 2.1: Diagram showing parts of the GPR system (Jol, 2009)
2.3 GPR Field Systems A GPR time-distance record can also be produced by making a series of fixed-mode measurements at a constant interval between traces on the surface. Fixed mode has been used in the survey. The transmitter and receiver antennas are moved independently in the fixed mode of operation, as shown in figure 2.2 and 2.3. This allows more flexibility of field operation than when the transmitter and receiver antennas are contained in a single box (Dobrin and Savit, 1988). For example, different polarization components can be recorded easily when the transmitter and receiver antennas are separate (Telford et al, 1990). In the fixed mode of operation, a trace is recorded at each discreet position of the transmitter and receiver antennas through the following sequence of events in the GPR system: 1) A wave is transmitted, 2) The receiver is turned on to receive and record the received signals, and 3) After a certain period of time the receiver is turned off. The resulting measurements that are recorded during the period of time that the receiver is turn14
Chapter Two
A Theoretical Background
ed on are called a trace (Tekeste et al, 2008). The idealized trace for this simple case consists of a direct pulse, and a single reflection from the layer. In the moving mode of operation, a radar wave is transmitted, received and recorded each time that the antenna has been moved. A fixed distance across the surface of the ground, or material is being investigated. Since a single record of a transmitted pulse is called a trace, the spacing between measurement points is called the trace spacing (Pearce et al, 2008). The trace spacing that is chosen should be a function of the target size and the objectives of the survey. Traces that are displayed side by side form a GPR time-distance record, or GPR cross section, which shows how the reflections vary in the subsurface. If the contrasts in electrical properties (e.g. changes in permittivity) are relatively simple, then the GPR time-distance record can be viewed as a two dimensional pseudo-image of the earth, with the horizontal axis the distance along the surface, and the vertical axis being the two-way travel time of the radar wave (Gizzi et al, 2010). The two-way travel time on the vertical axis can be converted to depth, if the permittivity (which can be converted to velocity) is known. The GPR time-distance record is the simplest display of GPR data that can be interpreted in terms of subsurface features.
Figure 2.2: Showing two types of GPR survey in the field (Bristow and Jol, 2003) 15
Chapter Two
A Theoretical Background
Figure 2.3: Shows GPR field work in fixed mode at location 1
2.4 GPR Signals and Soil Composition The penetration depth of GPR is determined by antenna frequency and the electrical conductivity of the earth materials being profiled. Because of rapid rates of signal attenuation, the penetration depth of GPR is greatly reduced in soils that have high electrical conductivity. Clays and salts provide ions and water facilitates the movement of charges
transforming
electromagnetic
energy
into
electrical
currents
limiting
the
propagation of the electromagnetic waves. Electrical conductivity in soils is directly related to the amount, distribution, and phase (liquid, solid, or gas) of the soil water, and the clay and soluble salt contents. Reduction observed in the depth of GPR signal penetration in soils that have high concentrations of calcium carbonate (Doolittle et al, 2007). Capillary retained water is sufficient to influence electrical conductivity even under dry soil moisture conditions. Soils contain various proportions of different clay minerals (e.g., members of Kaolin, Mica, Chlorite, Vermiculite, and Montmorillonite groups). The size, surface area, cation-exchange capacity (CEC), and water holding capacity of clay minerals vary greatly. Variations in electrical conductivity are attributed to differences in CEC associated with different clay minerals. Electrical conductivity increases with increasing CEC. Soils with clay fractions dominated by high CEC clays (e.g., Montmorillonite and 16
Chapter Two
A Theoretical Background
Vermiculite soil mineralogy classes) are more attenuating to GPR signals than soils with an equivalent percentage of low CEC clays (e.g., Kaolinitic, Gibbsitic, and Halloysitic soil mineralogy classes) (Doolittle et al, 2007). Soils classified as Kaolinitic, Gibbsitic, and Halloysitic characteristically have low CEC and low base saturation. As a general rule, for soils with comparable clay and moisture contents, greater depths of penetration can be achieved in highly weathered soils of tropical and subtropical regions that have kandic or oxic horizons than in soils of temperate regions that have argillic horizons. Compared with argillic horizons, kandic and oxic horizons have greater concentrations of low activity clays. Electrical conductivity is directly related to the concentration of dissolved salts in the soil solution, as well as to the type of exchangeable cations and the degree of dissociation of the salts on soil particles. The concentration of salts in the soil solution depends upon the degree of water-filled porosity, the soil texture, and the minerals found in soils. In semiarid and arid regions, soluble salts and exchangeable sodium accumulate in the upper part of some soil profiles. These salts, together with capillary retained water, produce high attenuation losses that restrict the radar's penetration depths (Doolittle et al, 2007). Because of their high electrical conductivity,
saline (saturated extract electrical
conductivity ≥ 4 mmhos cm−1) and sodic (sodium absorption ratio ≥ 13) soils are considered unsuited to GPR. Calcareous and gypsiferous soils are characterized by layers with secondary accumulations of calcium carbonate and calcium sulfate, respectively. These soils mainly occur in base-rich, alkaline environments in semi-arid and arid regions. High concentrations of calcium carbonate and/or calcium sulfate imply less intense leaching, prevalence of other soluble salts, greater quantities of inherited minerals from parent rock, and accumulations of specific mineral products of weathering. These properties contribute to the higher electrically conductivity of calcareous and gypsiferous soils (Jol, 2009). Depth of penetration of different geological materials is shown in figure 2.4.
17
Chapter Two
A Theoretical Background
Figure 2.4: Depth of penetration in the different geological materials (Google Search)
2.5 Instrumentation There are currently a number of different GPR systems on the market that are suitable for surveying. They all have slightly different configurations, as shown in Figure 2.5, they are all comprised of five main components 1) Control unit, 2) Transmitter, 3) Receiver, 4) Antennas, and 5) Interface, data storage, and display module. The control unit receives the survey parameters from the interface and generates the timing signals for the transmitter and receiver. It also receives the data from the receiver and does the initial processing before sending it to the storage device. In some systems the interface, data storage, displays and control unit are all incorporated into one unit (Emin et al, 2006). Data are collected at frequent intervals along a profile, such that the traces can be plotted side by side, creating a pseudo-section through the ground (Lowrie, 2007). In this research Ramac/GPR system has been used. In other systems, the control unit is separate and a laptop or palmtop computer is employed to enter the survey parameters, store the data, and provide real-time data display. On the command of the control unit, the transmitter generates the electromagnetic pulse that is emitted through an antenna connected to it (Mochales et al, 2008). The transmitter antenna pair determines the center frequency and bandwidth of the signal that is sent into the ground.
An antenna identical to that attached to the transmitter is attached to the
receiver. This antenna intercepts reflected energy and sends it to the receiver where it is amplified, digitized and sent to the control unit. The time versus received energy graph is 18
Chapter Two
A Theoretical Background
called a trace.
Figure 2.5: Shows different Parts of the GPR device
2.6 Data Processing and Interpretation The most important step in any GPR operation and after field work is the data processing. In the processing step, a number of filters are used such as Time gain, DC correction, Band pass, Automatic time control, Back ground removal, and Subtract mean trace. Time gain, equalizing amplitudes by applying a time-dependent gain function compensates for the rapid fall off in radar signals from deeper depths. DC correction is to remove the constant offset in each trace produced by imperfections of electronics. Band pass is removing the low and high frequency from the pulse. Back ground removal is supporting the weaker signals to appear clearly. After applying the important filters, it is converting the time domain section to the depth section by applying the suitable radar velocity, selected from the known charts and the soil velocity determined depending on the textural classification. Typical processing flow for GPR data is depicted in Figure 2.6. Data processing focuses on the highlighted areas: data editing, basic processing, advanced processing, and visualization interpretation processing. Processing is usually an iterative activity; data will 19
Chapter Two
A Theoretical Background
flow through the processing loop several times. Such processes include well-known seismic processing operations (Fisher et al, 1992) such as spatial and temporal filtering, selective muting, dip filtering, DE convolution, and velocity semblance analysis, as well as more GPR-specific operations such as background removal, multiple-frequency antenna mixing, and polarization is mixing. Migration is spatial deconvolution, which attempts to remove source and receiver directionality from reflection data. The goal is to reconstruct the geometrically correct radar reflectivity distribution of the subsurface. Topographic correction, because of the shallow exploration depth of GPR, compensating for topography is often important for minor surface variations, time-shifting data traces can largely compensate for topographic variations (Daniels, 2000). Batch processing with limited interactive control may be applied on large datasets after initial iterative testing on selected data samples has been performed (El Qady et al, 2005). Advanced data processing methods require varying degrees of interpreter bias to be applied and result in data that are significantly different from the raw input information. DE wow, the fields near the transmitter contain low-frequency energy associated with electrostatic and inductive fields, which decay rapidly with distance. This low frequency energy often yields a slowly time-varying component to the measured field data. This energy causes the base level of the received signal to bow up or down. This effect has become known as baseline “wow” in the GPR lexicon. The “wow” signal process can be suppressed by applying a high-loss temporal filter to the detected signal. This process is referred to as “dewow” (Boubaki et al, 2011) Time Gain, radar signals are very rapidly attenuated as they propagate into the ground. Signals from greater depths are very small when compared to signals from shallower depth. Simultaneous display of these signals requires conditioning before visual display. Equalizing amplitudes by applying a time-dependent gain function compensates for the rapid fall off in radar signals from deeper depths. DE convolution, the purpose of deconvolution is normally to maximize bandwidth and reduce pulse dispersion to ultimately maximize resolution (Goodman and Piro, 2013).
20
Chapter Two
A Theoretica l Background
Figure 2.6: GPR data processing flow chart (Jol, 2009)
2.7 Velocity Analysis 2.7.1 Using Hyperbolic Fitting The full utility of GPR data requires knowledge of how fast the signals travel in the material under investigation. Several techniques have been used such as CMP (common mid-point), WARR (wide angle reflection and refraction), known-depth-target, hyperbolic fitting to a local target and diffraction tail matching. All of these techniques require GPR measurements along a traverse where the geometry is varying in controlled fashion. In other words, the distance to a target varies in such estimations of velocity can be extracted (Van Dam, 2001).
2.7.2 CMP Analysis Ground penetrating radar (GPR) measures the time for signals in transmission and reflection from a target (Herman, 1997). In a CMP sounding the antenna geometry is vari21
Chapter Two
A Theoretical Background
ed in a controlled fashion so that signal arrival times follow predictable mathematical forms enabling velocity estimation (Yehia et al, 2004). The target depth or distance is determined by multiplying travel time by velocity in the host material, which is frequently unknown. Common mid-point (CMP) soundings are used to measure velocity and hence translate regular GPR time observations into reliable depth estimates (Hager and Carnevale, 2006). The below figure 2.7 shows how a CMP measurement is made and the principles of how radar signal arrivals are used to estimate velocity. Signals can follow a variety of paths from the transmitter (Tx) to the receiver (Rx).
Figure 2.7: Shows common Mid-Point analysis (CMD)
22
Chapter Two
A Theoretical Background
2.8 Methodology Ground Penetrating Radar profiles are similar in appearance to seismic reflection profiles, except that GPR data are acquired using transient electromagnetic (EM) energy reflection instead of acoustic energy and thus provide greater resolution. A short pulse of high frequency EM energy (10–1000MHz) is transmitted into the ground. When the signal encounters a contrast in material properties, some of the energy is reflected back to the surface due to a change in the bulk electrical properties of different subsurface lithology. The interface between these two layers may be characterized by bedrock contact, organicrich sediments, groundwater table, and changes in sediment grain size, mineralogy, and packing. A change in the dielectric constant (relative permittivity) of the sediment also affects the rate of attenuation of energy passing through the ground. The resolution and the penetration depth are based on the frequency and pulser voltage of the initial GPR signal and the material properties it travels through. Resolution ranges from sub-decimeter to greater than a meter and depths range from less than a meter to tens of meters (Smith and Jol, 1995).
23
Chapter Three Data Collection and Processing
C
Chapter Three
Data Collection and Processing
3.1 Preface The data is collected from different locations around Sulaimani City, and on the different types of soil derived from the different geological formations. In this study RAMAC/GPR Ground Penetrating Radar has been used with 100 MHZ of antenna. The software of Mala Ramac Ground Vision 1.4.2 has been used in the data collection while Rad. explorer is used in processing the collected data. The same parameter settings are used in collecting data such as Time window, Antenna separation, Trig interval, Number of sample, and Sample frequency and in a fixed mode of operation. As a result a large number profiles in a distance - time domains are obtained. The next step is data processing by using a set of filters such as Time varying gain, DC correction, Band pass, Background removal, Subtract mean trace and conversion of the time domain profiles to the depth profiles after applying suitable ground velocities. The last step is collecting of soil samples in each location, these samples are analyzing for mineralogical components, clay percent, and chemical composition. These data are collected in two different seasons for high and low soil moisture content. Some other minor data is collected as dip angle of the beds, coordination of traverses and distance measurements.
3.2 Data Collection The data is collected by the RAMAC/GPR device using ground vision software version 1.4.2, figure 3.1, in April and October of 2013. The Ground Vision is data acquisition software dedicated to the RAMAC/GPR mono or multi-channel systems. The ground Vision gives an easy interface to user, file management, printing and other key features. Each measurement and associated settings are stored in files. Filtering can be performed with the measurement or as post processing. 100 MHZ of antenna has been used, with the antenna separation of 1 m. Time window that defines the total trace length in time, trig intervals that control the distance scale. Sample frequency is the interval in which samples are taken over the trace length; a higher sampling frequency gives a shorter time window, the standard data set parameters used in the data collection are displayed in the table (3.1). The distance-time domain profiles obtained in a fixed mode of operation. Soil samples are collected in the field from each of the soil profile zones. The dip angles of the strata have been taken by geological compass of Silva type and coordination of the traverses is measu-
24
Chapter Three
Data Collection and Processing
red by GPS.
Figure 3.1: Shows the main window of the ground vision software, 1.4.2
Table 3.1: Shows a set of parameters used in data collection Frequency
Antenna
Time
(MHZ)
separation (m)
window(ns)
Trig interval
Sample
No. of
frequency
samples
(MHZ) 100
1
513
0.10
1055
541
3.3 Data Processing The important step after data collection is the processing of the obtained data by GPR device. The first step is processing of the radar profiles by using of the Rad. explorer soft25
Chapter Three
Data Collection and Processing
ware, version 1.41, as shown in figure 3.2. The most important filters applied to the radar grams are: Time gain, DC correction, Band pass, Automatic time control, Back ground removal, and Subtract mean trace. The time gain is equalizing the amplitudes of the signals at various depths by applying a timedependent gain function that compensates for the rapid fall off in radar signals especially from deeper depths. DC correction is applied to remove the constant offset in each trace produced by imperfections of electronics. The band pass is used in removing the low and high frequency from the pulse while back ground removal is supporting the weaker signals to appear clearly. The next step after applying the filters is the time domain conversion to the depth by applying a suitable velocity. Velocity is the important part of any data processing in the GPR system, can be estimated by common mid-point, charts and by fitting of the hyperbolas in the radar profiles. The soil velocity depends on the textural classification of the soils, as in table 3.2. The applied velocity for the depth conversion in this research is the velocity from the standard charts, as shown in table 3.3, after changing the relative permittivity to the velocity, equation (1). Velocity=1/√permittivity…………….. (1) (Jol, 2009)
Modeling is the important part in the processing; any profile is divided in to the soil part and rocks, in the modeling the velocity is applied in to the processing to the soil and rocks separately, as shown in figure 3.3. The collected soil samples are analyzed by X-ray diffraction for its clay and non-clay minerals. The chemical test was carried out for each sample to indicate the percentage of Na, K, Mg, and Ca by ICP device as well as texture analysis of samples to its clay. Sand and silt percentage was carried out.
26
Chapter Three
Data Collection and Processing
Figure 3.2: Shows the main window of the Rad. explorer, version 1.41
Table 3.2: Shows attenuation and Relative permittivity of the soils (Daniels, 2004) Material
Attenuation (dB/m)
Relative permittivity (R)
Soil firm
0.1-2
8-12
Soil, sandy dry
0.1-2
4-6
Soil, sandy wet
1-5
15-30
Soil, loamy dry
0.5-3
4-6
Soil, loamy wet
1-6
10-20
Soil, clayey dry
0.3-3
4-6
Soil, clayey wet
5-30
10-15
27
Chapter Three
Data Collection and Processing
Table 3.3: Shows Attenuation and Relative permittivity of materials (Daniels, 2004) Materials
Attenuation (dB/m)
Relative permittivity (R)
Air
0
1
Asphalt, dry
2-15
2-4
Asphalt, wet
2-20
6-12
Clay
10-100
2-40
Coal, dry
1-10
3.5-9
Coal, wet
2-20
8-25
Concret,dry
2-12
4-10
Concrete, wet
10-25
10-20
Fresh water
0.1
80
Fresh water ice
0.1-2
4
Granite, dry
0.5-3
5
Granite wet
2-5
7
Limeston,dry
0.5-10
7
Limestone, wet
10-25
8
Permafrost
0.1-5
4-8
Rock salt dry
0.01-1
4-7
Sand, dry
0.01-1
4-6
Sand, saturated
0.03-0.3
10-30
Sandstone, dry
2-10
2-3
Sandstone ,wet
10-20
5-10
Sea water
1000
81
Sea water ice
10-30
4-8
Shale, saturated
10-100
6--9
28
Chapter Three
Data Collection and Processing
Figure 3.3: Modeling of the Radar sections
3.4 Survey Design A certain design is selected for recording measurements on the approximate thicknesses of the soil equal to 4, 8, and 12 m. The operation depends on collected soils on an inclined bed rocks. The first step is finding dip of the beds for determination of the horizontal distance from the outcrop where the thickness of the soils are equal to 4, 8, and 12 m soil thickness,
as in shown in figure 3.4 and 3.5. Traverse one is located on the 4 m soil
thickness, second traverse is on the 8 m and third traverse is on the 12 m. The distance of each traverse from the bed rocks depends on the dip angle and they are always parallel to the strike direction. The length of each traverse is equal to 50 m, as in table 3.4 and 3.5. The soil thickness determined as in equation 1, 2 and 3. Tan Ɵ=4m/x1……. (1) Ɵ=Dip angle.
Tan Ɵ=8m/x2…….. (2)
X1, x2, x3=Distance from outcrops.
29
Tan Ɵ=12m/x3……… (3) 4m, 8m, 12=Soil thickness.
Chapter Three
Data Collection and Processing
Figure 3.4: The soil thickness calculation model in the field
Location 1 was placed on the Pilaspi Formation consisting of massive limestone, while the type of the soil is clay type which depends on the textural classification. Traverse distances from the outcrop are equal to 11.61 m, 23.23 m and 34.8 m according to the dip angle equal to (19) degrees for that the distance between traverses are widened in comparison to location 2. Location 2 was placed on the Lower Fars Formation, lithologically consisting of gypsum, anhydrite, limestone, salt, sandstone and marl, while type of the soil is sandy clay depending on the textural Classification. Traverses distances are equal to 3.86 m, 7.72 m and 11.58 m from the out crop according to its dip angle equal to (46) degrees in which the traverses distance are near. The type of the soil was gypsiferous because of present layers of gypsum. Location 3 was placed on the Shiranish Formation, composing of the limestone and marly limestone while the type of the soil is medium loam depending on textural classifica30
Chapter Three
Data Collection and Processing
tion. Traverse distances are equal to 6.92 m, 13.85 m and 20.78 m from the outcrops according to the dip angle equal to (30) degrees in which distance between traverses are widened in comparison to location 4. Location 4 is on the Kometan Formation, containing well bedded limestone, while the soil type is sandy clay loam depending on the textural classification. Traverse distances from outcrop are equal to 3.35 m, 6.7 m and 10 m respectively from the outcrops according to its dip angle equal to (50) degrees in which distance between traverses were near in comparison to the location 3.
Figure 3.5: 3D sketch of the field work at the location 2
Location 5 was placed on the Tanjero Formation consisting of silty marl, sandstone, conglomerate, marl, limestone respectively, while the soil type is loamy sand depending on the textural classification. Traverse distances are equal to 2.90 m, 5.81 m and 8.71 m from the outcrops according to its dip angle equal to (54) degrees leading to near distance between traverses. Location 6 was placed on the Red Bed Series consisting of reddish shale, silty shale, conglomeratic limestone, siltstone and conglomerate, and the soil type is sandy loam depending on the textural classification. Traverse distances are equal to 6.92 m, 13.85 m 31
Chapter Three
Data Collection and Processing
and 20.78 m from the outcrop according to its dip angle equal to (30) degrees for that the distance between traverses are widened. Location 7 was placed on the U. Fars Formation which includes calcareous Sandston, red and green mudstone with thin gypsum layer, and the soil type is clay loam depending on textural classification. Traverse distances are equal to 4.76 m, 9.53 m and 14.30 m from the outcrop according to the dip angle equal to (40) degrees. Table 3.4: Parent rock, formations and place of the GPR survey Location
Soil type
Parent rock of the soils
Formations
place
1
Clay
Limestone
Pilaspi
Gopala
2
Sandy clay
Sandstone, Gypsum,
Lower Fars
Takya
Shiranish
Kani Bardina
limestone, salt, anhydrite and marl. 3
Medium loam
Limestone, and marly limestone
4
Sandy clay loam
Limestone
Kometan
Darbarula
5
Loamy sand
Silty marle, sand,
Tanjero
Azaban
Red bed series
Sura Qalat
U. Fars
Qaradagh
conglomerate, limestone and sandistone 6
Sandy loam
Reddish shale, silty shale, conglomeratic limestone, siltstone and conglomerate.
7
Clay loam
Calcareous sandstone, red and green mudstone with thin Gypsum layer
32
Chapter Three
Data Collection and Processing
Table 3.5: Collected data from the field work Locations
Dip angle
Distance from the outcrop (m) T1 T2 T3 11.61 23.23 34.8
1
19°
2
46°
3.86
7.72
11.58
50
3
30°
6.92
13.85
20.78
50
4
50°
3.35
6.7
10
50
5
54°
2.90
5.81
8.71
50
6
30°
6.92
13.85
20.78
50
7
40°
4.76
9.53
14.30
50
33
Traverse length (m) 50
Coordination UTM E05.888255 N10.1333255 E.0..81255 N 10.805.255 E01..08255 N 10.10..255 E0.8308255 N10.83.0255 E0.0.31255 N 1010083255 E0..500255 N 10083.0255 E015.0.255 N 105081.255
Chapter Four The Effect of Soil Thickness on Radar Signals
D
Chapter Four
The Effect of Soil Thickness on Radar Signals
4.1 Preface The soil covers a vast area in Sulaimani. It has thickness ranging from zero to more than 150 m (Aziz, 2005) in the Bazian area, figure 4.1. The selected area is located within unstable part according to the Iraqi tectonic map, leading to a high weathering rate on the parental rock of the soil. Generally soils have a large effect on the attenuation of the radar signals (Doolittle et al, 2007 and Sucre et al, 2011), so with increasing of the soil thickness, attenuation of the radar signals increases too. Three traverses in each location are selected on different soil thicknesses that they are calculated by a special design in the investigated fields. As a result three radar sections have been obtained of different depth of penetration that it is more in the first traverse than that of the second and the third. Amplitude analyses have been applied by measuring signal amplitude at different depth.
Figure 4.1: Shows a large soil thickness in the Bazian area
4.2 Analysis of Soil Thickness Effect Soils are composed of different materials in which some of them are attenuating the radar signals as clay, water and salts. With increasing the soil thickness of these contents, radar signal attenuation also increases. This section includes soil thickness effect on the radar signals, for that three GPR traverses are determined that are located on the different
34
Chapter Four
The Effect of Soil Thickness on Radar Signals
soil thickness. This part calculated in dry (October of 2013) condition to subtract the moisture effect from the soil thickness calculation.
Location 1 It includes soil of clay type that has great effect on the radar signals, and limestone. The estimated radar velocity in the soil is equal to 8 cm/n, while in the limestone it is equal to 11.33 cm/ns in the dry condition. As a result, the depth of penetration (Table 4.1) is 26.5 m in the first traverse, figure 4.2, 25 m in the second traverse, figure (4.3), and 23.5 m in the third traverse, figure (4.4). Increasing the soil thickness from 4 to 8 m caused decreasing penetration depth by about 5.6 %, while the soil thickness is approaches to 12 m when the depth of penetration is decreased by about 11.3 %.
Table 4.1: Soil thickness and depth of penetration at location 1, (100 MHZ) Traverses
Soil thickness (m)
Depth of Penetration (m)
Decreasing depth of penetration %
1
4
26.5
-
2
8
25
5.6
3
12
23.5
11.3
Figure 4.2: Radar section at location 1, Traverse one (100MHZ) 35
Chapter Four
The Effect of Soil Thickness on Radar Signals
Figure 4.3: Radar section at location 1, Traverse two (100MHZ)
Figure 4.4: Radar section at location 1, Traverse three (100MHZ) 36
Chapter Four
The Effect of Soil Thickness on Radar Signals
Location 2 The soil is composed of sandy clay soil that has less effect than in the previous location, it is covering the rocks of Lower Fars Formation, mainly composed of sandstone, gypsum and marlstone. The estimated radar velocity and permittivity in the soil are equals to 8 cm/ns while in the rocks are equals to 16.3 cm/ns. As a result the obtained depth of penetration (Table 4.2) is 36 m in the first traverse, figure 4.5, 32 m in the second traverse, figure 4.6, 28 m in the third traverse, figure 4.7. Increasing the soil thickness from 4 to 8 m caused decreasing penetration depth by about 11.1 %, while when the soil thickness approaches 12 m when the depth of penetration is decreased by about 22.2 %.
Table 4.2: Soil thickness and depth of penetration at the location 2 (100 MHZ) Traverses
Soil thickness (m)
Depth of penetration (m)
Decreasing depth of penetration %
1
4
36
-
2
8
32
11.1
3
12
28
22.2
Figure 4.5: Radar section at the location 2, Traverse one (100MHZ) 37
Chapter Four
The Effect of Soil Thickness on Radar Signals
Figure 4.6: Radar section at the location 2, Traverse two (100MHZ)
Figure 4.7: Radar section at the location 2, Traverse three (100MHZ) 38
Chapter Four
The Effect of Soil Thickness on Radar Signals
Location 3 It includes soil of medium loam type that covered rocks of marly limestone and limestone of Shiranish Formation. The estimated radar velocity in the soil are equals to 8 cm/ns, while in the rocks equals to 11.33 cm/ns. As a result, the obtained depth of penetration (Table 4.3) is 25 m in the first traverse, figure 4.8, 24 m in the second traverse, figure 4.9, 23 m in the third traverse, figure 4.10. Increasing the soil thickness from 4 to 8 m caused decreasing penetration depth by about 4 %, while the soil thickness approaches 12 m when the depth of penetration is decreased by about 8 %.
Table 4.3: Soil thickness and depth of penetration at the location 3 (100 MHZ) Traverses
Soil thickness
Depth of penetration (m)
(m)
Decreasing depth of penetration %
1
4
25
-
2
8
24
4
3
12
23
8
Figure 4.8: Radar section at location 3, Traverse one (100MHZ). 39
Chapter Four
The Effect of Soil Thickness on Radar Signals
Figure 4.9: Radar section at location 3, Traverse two (100MHZ)
Figure 4.10: Radar section at location 3, Traverse three (100MHZ) 40
Chapter Four
The Effect of Soil Thickness on Radar Signals
Location 4 It includes soils of sandy clay loam type texturally that covered rocks of well bedded limestones that have less effect than in location 1. The estimated radar velocity in the soil is equal to 8 cm/ns, while in the rocks are equal to 11.33 cm/ns. As a result, the obtained depth of penetration (Table 4.4) is 24.5 m in the first traverse, figure 4.11, 24 m in the second traverse, figure 4.12, 23 m in the third traverse, figure 4.13. Increasing the soil thickness from 4 to 8 m caused decreasing penetration depth by about 2.04 %, while the soil thickness approaches to 12 m when the depth of penetration is decreased by about 4.08 %.
Table 4.4: Soil thickness and depth of penetration at the location 4 (100 MHZ) Traverses
Soil thickness (m)
Depth of penetration (m)
Decreasing depth of penetration %
1
4
24.5
-
2
8
24
2.04
3
12
23
4.08
Figure 4.11: Radar section at location 4, Traverse one (100MHZ) 41
Chapter Four
The Effect of Soil Thickness on Radar Signals
Figure 4.12: Radar section at location 4, Traverse two (100MHZ)
Figure 4.13: Radar section at location 4, Traverse three (100MHZ) 42
Chapter Four
The Effect of Soil Thickness on Radar Signals
Location 5 It includes soils of loamy sand that is more suitable with GPR in dry condition, which covered rocks of marl. The estimated radar velocity of the soil is equal to 8 cm/ns, while in the rocks are equal to 9.48 cm/ns. As a result, the obtained depth of penetration (Table 4.5) is 23 m in the first traverse, figure 4.14, 22.5 m in the second traverse, figure 4.15, 22 m in the third traverse, figure 4.16. Increasing the soil thickness from 4 to 8 m caused decreasing penetration depth by about 2.1 %, while the soil thickness approaches to 12 m when the depth of penetration is decreased by about 4.3 %.
Table 4.5: Soil thickness and depth of penetration at location 5 (100 MHZ) Traverses
Soil thickness (m)
Depth of penetration (m)
Decreasing depth of penetration %
1
4
23
-
2
8
22.5
2.1
3
12
22
4.3
Figure 4.14: Radar section at location 5, Traverse one (100MHZ) 43
Chapter Four
The Effect of Soil Thickness on Radar Signals
Figure 4.15: Radar section at location 5, Traverse two (100MHZ)
Figure 4.16: Radar section at location 5, Traverse three (100MHZ) 44
Chapter Four
The Effect of Soil Thickness on Radar Signals
Location 6 The soil is composed of sandy loam type that has less suitability than in the previous location that covered rocks of the reddish shale. The estimated radar velocity in the soil is equal to 8 cm/ns, while in the rock are equal to 10 cm/ns. The obtained depth of penetration (Table 4.6) is 24 m in the first traverse, figure 4.17, 23 m in the second traverse, figure 4.18, 22 m in the third traverse, figure 4.19. Increasing the soil thickness from 4 to 8 m caused decreasing penetration depth by about 4.1 %, while the soil thickness approaches to 12 m the depth of penetration is decreased by about 8.3 %.
Table 4.6: Soil thickness and depth of penetration at the location 6 (100 MHZ) Traverses
Soil thickness (m)
Depth of penetration (m)
Decreasing depth of penetration %
1
4
24
-
2
8
23
4.1
3
12
22
8.3
Figure 4.17: Radar section at location 6, Traverse one (100MHZ) 45
Chapter Four
The Effect of Soil Thickness on Radar Signals
Figure 4.18: Radar section at location 6, Traverse two (100MHZ)
Figure 4.19: Radar section at location 6, Traverse three (100MHZ) 46
Chapter Four
The Effect of Soil Thickness on Radar Signals
In this section, the decreasing percentage of the GPR penetration depth is calculated for each location and averaged. Appeared by increasing of 4 m of soil the GPR depth of penetration decreased by 4.8 % then calculated for 1 m of the soil thickness that equal to 1.2 % / m. Concluded that with increasing of the soil thickness GPR depth of penetration will decrease, for that suitability of the GPR is decreasing in those of the field investigation that are covered by large amount of the soil as in location 1 that located near the Gopala Village.
4.3 Amplitude Analysis Amplitude observation is very important in investigating the soil thickness effect on the radar signals. Amplitude attenuation increases with increasing of the soil thickness (Doolittle et al, 2007). It is recorded at each traverse for different depth by Rad. explorer 1.41, at the same signal trace. As a result, we noted that the amplitude attenuation or decreasing at depth is greater in the third (20 m) traverse in comparison to the first and second traverses.
Location 1 Amplitude of the radar signals is investigated from each traverse and they are shown in table 4.7 and figure 4.20. The signal amplitudes are recorded by Rad. explorer software at each 2 m intervals. Each traverse has its own depth of penetration that high in the first traverse while it is low in the third traverse. Signal amplitude attenuated at depth of 22 m in third traverse, while it is 0.01 in first and third traverse, because third traverse is on a greater soil thickness. The radar signals penetrated three different soil thicknesses, for that after 12 m of the depth, we are looking for the attenuation for observing the complete soil thickness effect on the radar signals. By observing of the data at the depth 14 m that it is after complete soil penetration, the amplitude is 0.04 in the first traverse, 0.03 in the second and 0.02 in the third. The signal attenuation from first to the third traverse is 0.02 units in which the difference in the soil thickness between them is 8 m. Sometime amplitudes decreased abruptly that it is may contact between two different materials. Amplitudes changed at the same depth which may refer to the rock particles or soil moisture in the soil.
47
Chapter Four
The Effect of Soil Thickness on Radar Signals Table 4.7: Amplitude in Traverse 1, 2 and 3 at location 1
Depth (m)
Amplitude, unit Traverse 1
Traverse 2
Traverse 3
2
1.38
1.22
1.25
4
1.06
1.04
1.05
6
0.51
0.42
0.40
8
0.23
0.24
0.25
10
0.09
0.08
0.09
12
0.04
0.05
0.03
14
0.04
0.03
0.02
16
0.03
0.02
0.02
18
0.03
0.02
0.01
20
0.01
0.01
0.01
22
0.01
0.01
0
24
0.01
0
0
26
0
0
0
48
Chapter Four
The Effect of Soil Thickness on Radar Signals
Amplitude, unit 0
0.2
0.4
0.6
0.8
1
1.2
1.4
2 4
6 8 10
Depth (m)
12
T1 T2
14
T3 16
18 20 22
24 26 28
Figure 4.20: Amplitude in traverse 1, 2 and 3 at different depth in location 1
Location 2 Amplitude is noted from each traverse at different depth as shown in table 4.8 and figure 4.21. The radar signals are recorded at each 2 m of depth interval by Rad. Explorer softwa49
Chapter Four
The Effect of Soil Thickness on Radar Signals
re. Different depths of penetration were recorded for each traverse with higher depth in the first traverse and lower in the last traverse. The signals attenuated at depth of 22 m in the third traverse, while it is 0.03 and 0.02 units in the first and second traverse, because third traverse is on a greater soil thickness. As in the previous location, the radar signals are penetrating three different soil thicknesses respectively, for that after 12 m of depth the signals attenuation is observed. The radar signal attenuation at the depth of 14 m is 0.06 in the first traverse, 0.05 in the second and 0.03 in the third, for that the signal attenuation is 0.03 units from first to the
third traverse, in which the soil thickness difference is 8 m
between them. At depth of 10 m signals changed abruptly which may refer to the contact of two different materials. Signals for the same depth are changed that may related to the boulders and rock particles or moisture in soils.
Table 4.8: Amplitude in Traverse 1, 2 and 3 at location 2 Depth (m)
Amplitude, unit Traverse 1
Traverse 2
Traverse 3
2
0.50
0.56
0.45
4
0.24
0.23
0.22
6
0.20
0.24
0.22
8
0.20
0.18
0.19
10
0.11
0.10
0.08
12
0.09
0.07
0.07
14
0.06
0.05
0.03
16
0.05
0.04
0.03
18
0.04
0.03
0.01
20
0.03
0.02
0.01
22
0.03
0.02
0
24
0.03
0
0
26
0
0
0
28
0
0
0
50
Chapter Four
The Effect of Soil Thickness on Radar Signals
Amplitude, unit 0
0.1
0.2
0.3
0.4
0.5
0.6
2
4 6
8 10
Depth (m)
12
T1 T2
14
T3 16 18 20
22 24
26 28
Figure 4.21: Amplitude in traverse 1, 2 and 3 at different depth in location 2
Location 3 Amplitude is observed from each traverse in different depths, as shown in table 4.9 and figure 4.22. The radar signal amplitudes were observed at 2 m of depth intervals from the used software. In each location, different depth of penetration was obtained that is higher
51
Chapter Four
The Effect of Soil Thickness on Radar Signals
in the first traverse. Amplitude at depth of 24 m is attenuated in the third traverse, while it is 0.05 and 0.01 in the first and second traverses, because third traverse is on a greater soil thickness. As usual three different soil thicknesses penetrated by the radar signals respectively for that after 12 m of depth signal attenuation can be observed after complete soil penetration. The radar signals at the depth of the 14 m is 0.08 in the first, 0.06 in second and 0.04 in the last traverse. The difference in the signals amplitude between the first and last traverse is 0.04 of 8 m soil thickness difference. Sometime amplitudes changed abruptly which may refer to the contact between two different materials. Amplitudes near the surface are not same for three traverses that may related to the boulders and soil moisture.
Table 4.9: Amplitude in Traverse 1, 2 and 3 at location 3 Depth (m)
Amplitude, unit Traverse 1
Traverse 2
Traverse 3
2
1.82
1.92
1.63
4
0.30
0.31
0.32
6
0.15
0.15
0.14
8
0.12
0.11
0.10
10
0.11
0.11
0.09
12
0.08
0.08
0.04
14
0.08
0.06
0.04
16
0.06
0.05
0.04
18
0.06
0.03
0.03
20
0.04
0.03
0.02
22
0.03
0.01
0.02
24
0.05
0.01
0
26
0.04
0
0
52
Chapter Four
The Effect of Soil Thickness on Radar Signals
Amplitude, unit 0
0.5
1
1.5
2
2
4
6
8
10 T1
Depth (m)
12
T2 T3
14
16
18
20
22
24
26
Figure 4.22: Amplitude in traverse 1, 2 and 3 at different depth in location 3
Location 4 Amplitude investigated from each traverse of different depth as shown in table 4.10 and figure 4.23. The radar signal amplitudes were obtained by the Rad. Explorer software at 2 m depth intervals. Different depth of penetration was obtained that is lower in the third tra53
Chapter Four
The Effect of Soil Thickness on Radar Signals
verse than in other traverse. Amplitudes attenuated at depth of 22 m in the third traverse, while it is 0.01 in the first and second traverse, because third traverse is on a greater soil thickness. The radar signals penetrated three different soil thicknesses respectively for that the signal attenuation as usual observed after 12 m of depth. The radar signals were recorded at the depth of 14 m appeared that the signal amplitude is 0.02 in the first, 0.01 in second and third traverse. The signal attenuation difference between the first and third traverse is 0.01 that the soil thickness difference between them is 8 m. In some depth amplitudes changed quickly that may relate to the contact between two different materials. Near the surface amplitudes are not same for the same depth that may refer to the particles and boulders in it.
Table 4.10: Amplitude at Traverse 1, 2 and 3 at location 4 Depth (m)
Amplitude, unit Traverse 1
Traverse 2
Traverse 3
2
0.70
0.76
0.63
4
0.46
0.44
0.47
6
0.20
0.18
0.18
8
0.03
0.02
0.02
10
0.03
0.02
0.01
12
0.02
0.01
0.01
14
0.02
0.01
0.01
16
0.02
0.01
0.01
18
0.01
0.01
0.01
20
0.01
0.01
0.01
22
0.01
0.01
0
24
0.01
0
0
26
0
0
0
54
Chapter Four
The Effect of Soil Thickness on Radar Signals
Amplitude, unit 0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
2
4
6
8
10 T1
Depth (m)
12 T2
14
16
T3
18
20
22
24
26
Figure 4.23: Amplitude in traverse 1, 2 and 3 at different depth in location 4
Location 5 Amplitude is noted from each traverse of different depth as shown in table 4.11 and figure 4.24. The amplitude of the signals was collected by the Rad. Explorer software of 2 m intervals. As in the previous locations, different depth of penetration was obtained that 55
Chapter Four
The Effect of Soil Thickness on Radar Signals
higher in the first traverse than in other. Signals attenuated at depth of 20 m in the third traverse, while it is 0.03 and 0.01 in the first and second traverses, because third traverse is on a greater soil thickness. Three different soil thicknesses were selected respectively, for that the signal attenuation was observed at the depth of 14 m depth as in other locations. The signal amplitude is 0.06 in the first, 0.04 in the second and 0.03 in the third, for that from the first to the third traverse after increasing of 8 m soil the signal attenuation was 0.03. Amplitudes changed abruptly near surface which may contact between two materials or change in soil moisture. Also near surface for the same depth amplitudes changed because of boulders and rock particles.
Table 4.11: Amplitude in Traverse 1, 2 and 3 at location 5 Depth (m)
Amplitude, unit Traverse 1
Traverse 2
Traverse 3
2
0.41
0.42
0.40
4
0.36
0.36
0.32
6
0.20
0.19
0.18
8
0.17
0.15
0.16
10
0.15
0.14
0.15
12
0.04
0.03
0.02
14
0.06
0.04
0.03
16
0.04
0.03
0.02
18
0.04
0.02
0.01
20
0.03
0.01
0
22
0.02
0
0
24
0
0
0
26
0
0
0
56
Chapter Four
The Effect of Soil Thickness on Radar Signals
Amplitude, unit 0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
2
4
6
8
10 T1
Depth (m)
12
T2 T3
14
16
18
20
22
24
26
Figure 4.24: Amplitude in traverse 1, 2 and 3 at different depth in location 5
Location 6 Amplitude of the radar signals is noted from each traverse in different depth as shown in table 4.12 and figure 4.25. The software of Rad. Explorer is used in the recording of the si-
57
Chapter Four
The Effect of Soil Thickness on Radar Signals
gnal amplitudes at 2 m intervals. The depths of penetration were different that it is high in the first traverse than in other. Amplitudes are attenuated in second and third traverse at depth of 22 m while it is 0.02 units in the first, because second and third traverses are on a greater soil thickness. The radar signals penetrated different soil thickness, for that the signal attenuation observed after 12 m depth as in 14 m, it is 0.06 in the first, 0.05 in the second and 0.02 in the last traverses respectively. Attenuation in the amplitude from the first traverse to the third in the depth of 14 m is 0.04 in which difference in the soil thickness between them is 8 m. Abrupt change in amplitudes may refer to change from a material to other or soil moisture. Also there is a change in amplitudes for the same depth near surface because of boulders and rock particles.
Table 4.12: Amplitude in Traverse 1, 2 and 3 at location 6 Depth (m)
Amplitude, unit Traverse 1
Traverse 2
Traverse 3
2
0.42
0.46
0.40
4
0.41
0.36
0.32
6
0.32
0.30
0.31
8
0.14
0.13
0.15
10
0.12
0.10
0.11
12
0.06
0.08
0.07
14
0.06
0.05
0.02
16
0.05
0.04
0.02
18
0.03
0.02
0.01
20
0.02
0.01
0.01
22
0.02
0
0
24
0
0
0
58
Chapter Four
The Effect of Soil Thickness on Radar Signals
Amplitude, unit 0
0.1
0.2
0.3
0.4
0.5
2
4
T1 6 T2
8
10
T3
Depth (m)
12
14
16
18
20
22
24
26
Figure 4.25: Amplitude in traverse1, 2 and 3 at different depth in location 6
Location 7 Amplitude observed from each traverse in different depth as shown in table 4.13 and figure 4.26. As in the previous locations the Rad. Explorer is used in the amplitude calcula59
Chapter Four
The Effect of Soil Thickness on Radar Signals
tion at 2 m interval. High depth of penetration is recorded in the first traverse than in the second and third traverses. Signal amplitude attenuated at depth of 22 m in the third traverse, while it is 0.05 and 0.02 in the first and second traverses, because third traverse is on a greater soil thickness. The radar signals were penetrated three soil thicknesses, for that the signal attenuation is observed after penetrating of 12 m as in 14 m in which amplitude is 0.14 in first, 0.12 in the second and 0.10 in the third traverse. The amplitude attenuation from the first traverse to the third traverse is equal to 0.04 in which 8 m of soil is the difference between them. Amplitudes changed abruptly that may relate to the contact between two different materials. There is a change in amplitudes for the same depth near surface that may refer to the abrupt change in the soils.
Table 4.13: Amplitude in Traverse 1, 2 and 3 at location 7 Depth (m)
Amplitude, unit Traverse 1
Traverse 2
Traverse 3
2
5.08
4.81
4.37
4
0.55
0.40
0.42
6
0.33
0.30
0.30
8
0.27
0.26
0.25
10
0.23
0.23
0.20
12
0.20
0.21
0.21
14
0.14
0.12
0.10
16
0.12
0.10
0.08
18
0.08
0.06
0.06
20
0.07
0.05
0.03
22
0.05
0.02
0
24
0.02
0
0
26
0
0
0
60
Chapter Four
The Effect of Soil Thickness on Radar Signals
Amplitude, unit 0
1
2
3
4
5
6
2
4
6
8
10 T1
Depth (m)
12
T2 T3
14
16
18
20
22
24
26
Figure 4.26: Amplitude at traverse1, 2 and 3 at different depth in location 7
61
Chapter Four
The Effect of Soil Thickness on Radar Signals
Amplitudes at the depth of 14 m of depth were observed between traverse 1 and 3, as shown in table 4.14, because the maximum soil thickness is 12 m, for that the amplitude attenuation observed after complete soil thickness penetration by radar waves. The decreasing percentage in amplitude is analyzed between first and third traverse because soil thickness is 4 m in the first and 12 m at the third traverse. The calculated decreasing percentage is after increasing of 8 m of soil, the average decreasing of amplitude is 49.3 % for 8 m of soil, can be calculated for 1 m of soil that equal to 6.1 % / m. The decreasing percentage is high in some places as in the last location that may refer to the other parameters in the soil as Montmorillonite mineral that high in the last location, or soil moisture.
Table 4.14: Showing of the amplitude decreasing percentage after increasing of 8 m soil Amplitude at depth 14 m Locations
Traverse 1
Traverse 3
Decreasing %
1
0.04
0.02
50 %
2
0.06
0.03
50 %
3
0.08
0.04
50 %
4
0.02
0.01
50 %
5
0.06
0.03
50 %
6
0.06
0.02
66.6 %
7
0.14
0.10
28.5 % Average= 49.3 %
62
Chapter Four
The Effect of Soil Thickness on Radar Signals
4.4 Spectra Analysis This part of the current study is dealing with the spectra analysis of the signal amplitudes in which the amplitude percentage is shown near the surface to the depth. The amplitude percentages are shown against depth which is taken from the processed sections. The purpose of this analysis is to investigate the signal amplitude percentage especially at the depth of three traverses that are located on the three different soil thicknesses. In each location three traverses are performed for that three amplitude spectra are obtained that are recorded by Rad. explorer software. Observation focused on the amplitude percentage at depth and lower part of the spectra, because this part penetrated three soil thicknesses completely. In each spectra the amplitude percentage are obtained in a specific depth as in 18 m appeared that the amplitude percentage at that depth is higher in the first traverse in comparison to the other. In location 1, the spectra analysis performed in three traverses as shown in figure 4.27. Appeared that the amplitude percentage at depth of 18 m is equal to 5 % in the first, 4% in the second and 3 % in the third traverse. Concluded that this change in amplitude is referring to the difference in the soil thickness. In location 2, three traverses are determined with their spectra of the amplitude of different depth as shown in figure 4.28. The determined amplitude percentage at the depth of 18 m is equal to 4 % in first, 3 % in the second and 2 % in the third. As in the previous location, this change refers to the soil thickness change, but a change from this location to the previous location is referring to the soil types in those locations. In location 3, three amplitude spectra are also obtained as shown in figure 4.29. The amplitude percentage in depth of 18 m is equal to 6 % in the first, 5 % in the second and 3 % in the third traverse; this is caused by the soil thickness change. In location 4, the amplitude percentage is observed from the spectra analysis as shown in figure 4.30. The amplitude percentage in depth of 18 is equal to 4 % in the first, 3 % in the second and 2 % in the third traverse. In location 5 the spectra analysis also carried out for each traverse as shown in figure 4.31. The percentage of the amplitude in depth of 18 m is equal to 4 % in first, 3 % in the second and 2 % in the third. In location 6 amplitude percentages are also recorded from the spectra analysis as shown in figure 4.32. The signal amplitude percentage in depth of 18 m is equal to 5% in 63
Chapter Four
The Effect of Soil Thickness on Radar Signals
the first, 3 % in the second and 3 % in the third traverse. In the last location amplitudes are also observed from the spectra by the Rad. Explorer software as shown in figure 4.33. The amplitude in depth of 18 m is equal to 4% in the first, 3 % in the second and 2 % in the third traverse. Maximum amplitudes are determined as shown in table 4.15, appeared that the maximum amplitude is in the location II and IV. The difference in the maximum amplitude between traverse I and III are determined because the soil thickness difference between them is 8 m, appeared that there is a change in amplitude between them, the maximum difference is 19 % in the third location, as shown in table 4.16.
Figure 4.27: Spectra analysis at location 1 64
Chapter Four
The Effect of Soil Thickness on Radar Signals
Figure 4.28: Spectra analysis at location 2 65
Chapter Four
The Effect of Soil Thickness on Radar Signals
Figure 4.29: Spectra analysis at location 3 66
Chapter Four
The Effect of Soil Thickness on Radar Signals
Figure 4.30: Spectra analysis at the location 4 67
Chapter Four
The Effect of Soil Thickness on Radar Signals
Figure 4.31: Spectra analysis at the location 5 68
Chapter Four
The Effect of Soil Thickness on Radar Signals
Figure 4.32: Spectra analysis at the location 6 69
Chapter Four
The Effect of Soil Thickness on Radar Signals
Figure 4.33: Spectra analysis at the location 7 70
Chapter Four
The Effect of Soil Thickness on Radar Signals
Table 4.15: Maximum and minimum amplitude % in the spectra analysis Locations
Amplitude % (Maximum-Minimum) Traverse 1
Traverse 2
Traverse 3
Max.
Min.
Max.
Min.
Max.
Min.
1
90
3
84
2
80
1
2
100
2
99
2
99
1
3
86
2
73
1
67
1
4
100
3
99
2
99
1
5
85
3
81
2
81
1
6
76
3
74
2
74
1
7
81
2
75
3
74
1
Table 4.16: Difference in maximum amplitude between First and third traverse Locations
Maximum amplitude percentage Traverse 1
Traverse 3
Difference
1
90
80
10
2
100
99
1
3
86
67
19
4
100
99
1
5
85
81
4
6
76
74
2
7
81
74
7
71
Chapter Five The Effect of Soil Moisture on Radar Signals
E
Chapter Five
The Effect of Soil Moisture on Radar Signals
5.1 Preface Information about soil moisture that has great effect on the radar signals is very important for the users of Ground Penetrating Radar. GPR ground wave methods can be used to collect many more water content estimates than could be obtained using conventional point measurement techniques, because GPR data can be acquired with a sampling increment as small as 1 cm (Grote et al, 2010). The soil moisture has effects on GPR depth of penetration and performance, with increasing of the soil moisture content that leads to high reflection coefficient but low depth of penetration (Giraldo and Gale, 2011). Similarly, the permittivity of water bearing soil is strongly influenced by its water content. Ground Penetrating Radar on the same traverses and by using the same parameters was carried out in two seasons, the first was in April of 2013 that the soil moisture is high and second in October of 2013 with low moisture content, figure 5.1. As a result, different depth of penetration was obtained that was lower in the condition of high soil moisture content and high in the low moisture content. Amplitude of both conditions were analyzed, high amplitudes is in the dry than those in the wet condition were obtained. Spectra of each moisture content is investigated, the high amplitude percentage in the dry condition was recorded.
Figure 5.1: Shows dry and wet condition of the survey at the same site in location 1 72
Chapter Five
The Effect of Soil Moisture on Radar Signals
5.2 Soil Moisture Effect on the Depth of Penetration Ground Penetrating Radar is operated in two different conditions of soil wet and dry, as a result different depths of penetration are obtained, as shown in table 5.1. High depth of penetration is obtained in the dry condition in comparison to the wet condition, so the best case for GPR investigation is in the dry condition. Radar sections of this chapter are depending on the second traverse of each location.
Location 1 The survey is performed in two different soil moisture conditions of the same parameter setting and on the same location. Two GPR sections are obtained. After entering the suitable velocity, different depths of penetration are obtained which are higher in the dry condition. The estimated radar velocity of the soil is equal to 8 cm/ns and 13 of permittivity, while in the rock it is equal to 11.33 cm/ns and 7 of permittivity in the dry condition. In the wet case, soil radar velocity is equal to 7.5 cm/ns and 16 of permittivity, while in the rock it is 10.6 cm/ns and 8 of permittivity. As a result, 25 m depth of penetration was obtained in the dry condition (figure 4.3) and 23 m in the wet case (figure 5.2). The percentage of decreasing depth of penetration is equal to 8 % from dry to the wet condition.
Location 2 As in the previous location, GPR survey is investigated in the dry and wet soil conditions, as a result two different depths of penetration were obtained with higher depth in the dry condition. The depth of penetration in dry condition or wet condition is differing from a location to another because of the difference in the soil moisture. The estimated radar velocity in the soil is equal to 8 cm/ns and 13 of permittivity, while in the rocks it is equal to 16.3 cm/ns and 3.5 of permittivity, in the dry condition. In the wet case, velocity in the soil is equal to 7.5 cm/ns and 16 of permittivity, while in rocks it is 10.95 cm/ns and 7.5 of permittivity. As a result, 32 m of depth was obtained in the dry condition (figure 4.6) and 23 m in the wet condition (figure 5.3). The percentage of decreasing in depth of penetration is equal to 28.1 % between dry and wet conditions.
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Figure 5.2: Radar section at location one, traverse two, wet condition (100MHZ)
Figure 5.3: Radar section at location two, traverse two, wet condition (100MHZ) 74
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Location 3 In the dry and wet conditions, the GPR survey was performed for that two different depths of penetration were obtained that were higher in the dry condition because saturated soils have a high electrical conductivity that is unsuitable with the electromagnetic waves. The estimated radar velocity in the soil is equal to 8 cm/ns and 13 of permittivity, while in rocks it is equal to 11.33 cm/ns and 7 of permittivity in the dry condition. In the wet case velocity in soil is equal to 7.5 cm/ns and 16 of permittivity, while in rocks it is equal to 10.6 cm/ns and 8 of permittivity. As a result, 24 m depth obtained in the dry condition (figure 4.9) and 23.5 m in the wet case (figure 5.4). Decreasing of the depth between dry and wet condition is 2.08 %.
Location 4 As previously mentioned the GPR was performed in two soil moisture conditions, because the soil moisture increases the soil electrical conductivity by the free electron charges that are unsuitable with the GPR. As a result high depth of penetration is obtained in the dry condition. The estimated radar velocity in the soil is equal to 8 cm/ns and 13 of permittivity, while in rocks 11.33 cm/ns and 7 of permittivity in the dry condition. In the case of wet condition, the soil radar velocity is equal to 7.5 cm/ns and 16 of permittivity, while in rocks 10.6 cm/ns and 8 of permittivity. As a result, 23.5 m of depth obtained in the dry condition (figure 4.12) and 22 m in the wet condition (figure 5.5). Decreasing of depth is 6.3 % from dry to the wet condition.
Location 5 In this location as in the previous locations, the survey was investigated in two different soil moisture conditions because water holding capacity of the soils are different from a soil to another or from a location to another for that the depth of penetration is different from a location to another. The estimated radar velocity in the soil is 8 cm/ns and 13 of permittivity, in rocks 9.48 cm/ns and 10 of permittivity in the dry condition. In the wet condition soil velocity is 7.5 cm/ns and 16 of permittivity, in rocks 8.6 cm/ns and 12 of permittivity. As a result, 22.2 m of depth obtained in the dry condition (figure 4.15) and 20.5 m in the wet condition (figure 5.6). Decreasing of depth is 11.1 % from dry to the wet condition. 75
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Figure 5.4: Radar section at location three, traverse two, wet condition (100MHZ)
Figure 5.5: Radar section at location four, traverse two, wet condition (100MHZ) 76
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Figure 5.6; Radar section at location five, traverse two, wet condition (100MHZ)
Location 6 Higher depth of penetration is obtained in the dry condition because of lower electrical conductivity than in the wet condition. The estimated radar velocity in the soil is 8 cm/ns and 13 of permittivity, in rocks 10 cm/ns and 9 of permittivity in the dry condition. In the wet condition, soil velocity is 7.5 cm/ns and 16 of permittivity; in rocks is 9.04 cm/ns and 11 of permittivity. As a result, 23 m of depth is obtained in the dry condition (figure 4.18) and 20.5 m in the wet condition (figure 5.7). Depth of penetration decreases by 10.8% from dry to wet condition.
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Figure 5.7: Radar section at location six, traverse two, wet condition (100MHZ)
From this part of the study of the soil moisture effect on the GPR depth of penetration result in that the depth of penetration being higher in the dry condition than in the wet condition. In each location three traverses are performed. Here the second traverse is selected for the whole locations as a result of different depths of penetration being obtained as shown in figure (5.8). The decreasing percentage in depths is determined in each location from dry to the wet condition as shown in table (5.1), and then they average appeared that the decreasing percentage from dry to wet is 11.06 %. The decreasing percentage changed from a location to other that may due to soil moisture amount in that soil, that more in some soil, may refer to their soil texture.
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The Effect of Soil Moisture on Radar Signals Table 5.1: Depth of penetration in dry and wet conditions
Locations
Depth of penetration (m)
Decreasing %
Dry condition
Wet condition
1
25
23
8
2
32
23
28.1
3
24
23.5
2.08
4
23.5
22
6.3
5
22.5
20.5
11.1
6
23
20.5
10.8 Average= 11.06 %
Locations
1
2
3
4
5
6
0
5
Depth of penetration (m)
10
Dry condition 15
Wet condition
20
25
30
35
Figure 5.8: Shows the maximum depth of penetration in dry and wet conditions
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5.3 Amplitude Analysis The amplitude analyses were carried out in both dry and wet conditions at the same location. Amplitude of each location is analyzed and it is obtained that the amplitude is high in the dry condition in comparison to the wet condition.
Location 1 Amplitudes were observed in dry and wet conditions in 2 m intervals of the depth, as shown in table (5.2). It appeared that the signal amplitudes in dry condition were higher than in the wet condition in any point of depth as shown in figure (5.9). The amplitude decreasing percentages are determined at any 2 m intervals that they are equal to 18.1 %100 % from the dry to the wet condition then they are averaged equal to 53.8 %. The total attenuation of amplitude is observed in the penetration depth equal to 24 m in dry condition and 22 m in wet condition. Sometime there is an abrupt change in the amplitudes or decreasing percentage that may refer to the amount of the soil moisture.
0
0.2
0.4
Amplitude, unit 0.6 0.8 1
1.2
1.4
1.6
2 4 6 8
Depth (m)
10 Dry condition
12
Wet condition
14 16 18 20 22 24 26
Figure 5.9: Amplitude in dry and wet condition in different depths at location 1 80
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Table 5.2: Amplitude in dry and wet condition at location 1 Depth (m)
Amplitude, unit Dry condition
Wet condition
Decreasing %
2
1.50
1.22
18.6
4
1.27
1.04
18.1
6
0.53
0.42
20.7
8
0.50
0.24
52
10
0.42
0.08
80.9
12
0.08
0.05
37.5
14
0.09
0.03
66.6
16
0.06
0.02
66.6
18
0.05
0.02
60
20
0.04
0.01
75
22
0.02
0.01
50
24
0.02
0
100 Average= 53.8 %
Location 2 In 2 m intervals of depth amplitudes are recorded in both conditions as shown in table 5.3, and it appears that the amplitudes at any points of the depth are higher in the dry condition than in the wet condition. This refers to the difference in electrical conductivity, as shown in figure 5.10. As in the previous location, the amplitude which is decreasing is calculated ranging from 14.2 %-100 % and they are averaged equal to 68.7 %. The total attenuation in the dry condition is in depth of 32 m and 22 m in the wet condition. 81
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Decreasing percentage is different in depth intervals because of change in soil moisture.
Table 5.3: Amplitude in dry and wet condition at location 2 Depth (m)
Amplitude, unit Dry condition
Wet condition
Decreasing %
2
3.14
0.56
82.1
4
2.5
0.23
90.8
6
0.28
0.24
14.2
8
0.27
0.18
33.33
10
0.18
0.10
44.44
12
0.15
0.07
53.33
14
0.11
0.05
54.54
16
0.08
0.04
50
18
0.06
0.03
50
20
0.06
0.02
66.66
22
0.05
0.02
60
24
0.05
0
100
26
0.03
0
100
28
0.02
0
100
30
0.02
0
100
32
0.01
0
100 Average=68.7 %
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0
The Effect of Soil Moisture on Radar Signals
0.5
1
Amplitude, unit 1.5 2
2.5
3
3.5
2
4 6
8 10 12
Depth (m)
14 Dry condition
16
Wet condition
18 20
22 24
26 28 30 32 34
Figure 5.10: Amplitude in dry and wet condition in different depths at location 2
Location 3 In both dry and wet conditions amplitude of the signals are determined in 2 m intervals of depth as shown in table 5.4. Higher amplitude in the whole depth is recorded in the dry condition than in the wet condition as shown in figure 5.11. The decreasing percent in amplitude in any depth from dry to the wet condition is determined ranging from 11.1 %-75 % then averaged
is equal to 33.87 %. The total attenuation of the amplitude is
equal to 24 m in the dry and wet conditions. The soil moisture amount in depth intervals 83
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Leading to decreasing percentages are different.
Table 5.4: Amplitude in dry and wet condition at location 3 Depth (m)
Amplitude, unit Dry condition
Wet condition
Decreasing %
2
2.37
1.92
18.9
4
0.52
0.31
40.3
6
0.30
0.15
50
8
0.18
0.11
38.8
10
0.15
0.11
26.6
12
0.09
0.08
11.1
14
0.07
0.06
14.2
16
0.06
0.05
16.6
18
0.05
0.03
40
20
0.04
0.03
25
22
0.04
0.01
75
24
0.02
0.01
50 Average=33.87 %
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0
The Effect of Soil Moisture on Radar Signals
0.5
Amplitude, unit 1 1.5
2
2.5
2
4 6 8 10
Depth (m)
12
Dry condition Wet condition
14 16 18 20 22 24 26
Figure 5.11: Amplitude in dry and wet condition in different depths at location 3
Location 4 The radar signal amplitudes are recorded in both conditions, dry and wet condition in any 2 m intervals as shown in table 5.5 with higher amplitude in dry condition as shown in figure 5.12. The decreasing percentage from the dry to the wet conditions is determined minimum equal to 0 and maximum equal to 100 %. They are then averaged equal to 61.4
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%. The total attenuation of the radar signals in the dry condition is recorded in depth of 24 m and 22 m in the wet condition. Soil moisture amount differences leading a change in decreasing percentage of depth intervals.
Table 5.5: Amplitude in dry and wet condition at location 4 Depth (m)
Amplitude, unit Dry condition
Wet condition
Decreasing %
2
1.54
0.76
50.6
4
0.70
0.44
37.1
6
0.22
0.18
18.1
8
0.20
0.02
90
10
0.20
0.02
90
12
0.19
0.01
94.7
14
0.15
0.01
93.3
16
0.06
0.01
83.3
18
0.05
0.01
80
20
0.01
0.01
0
22
0.01
0.01
0
24
0.01
0
100 Average=61.4 %
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Chapter Five
0
The Effect of Soil Moisture on Radar Signals
0.5
Amplitude, unit 1
1.5
2
2 4
6 8
10
Depth (m)
12
Dry condition Wet condition
14
16 18
20 22 24
26
Figure 5.12: Amplitude in dry and wet condition in different depths at location 4
Location 5 The radar signal amplitudes are observed in the dry and wet conditions in any 2 m of depth intervals as shown in table 5.6 and figure 5.13 with higher amplitude in dry than in the wet condition. The decreasing percentage of the amplitudes are also calculated near the surface to the depth that range from 36.3 %- 100 % then they averaged equal to 70.4 %. 87
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The total radar signal attenuation recorded at depth of 22 m in dry and 20 m in the wet condition. As in other locations soil moisture amount affected the decreasing percentage in depth intervals.
Table 5.6: Amplitude in dry and wet condition at location 5 Depth (m)
Amplitude, unit Dry condition
Wet condition
Decreasing %
2
1.82
0.42
76.9
4
1.37
0.36
73.7
6
0.30
0.19
36.6
8
0.25
0.15
40
10
0.22
0.14
36.3
12
0.16
0.03
81.2
14
0.15
0.04
73.33
16
0.14
0.03
78.5
18
0.14
0.02
85.7
20
0.14
0.01
92.8
22
0.10
0
100 Average=70.4 %
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0
The Effect of Soil Moisture on Radar Signals
0.5
Amplitude, unit 1
1.5
2
2
4
6
8
Depth (m)
10 Dry condition
12
Wet condition
14
16
18
20
22
24
Figure 5.13: Amplitude in dry and wet condition in different depths at location 5
Location 6 In any 2 m intervals radar signal amplitudes are recorded in both conditions as shown in table 5.7 and higher amplitude in any depth in the dry condition than in the wet condition as shown in figure 5.14. The decreasing percentage of the radar signals are also investigated for any depth ranging from 0-100 % from dry to the wet conditions and then
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averaged equal to 49.2 %. The total signal attenuation is recorded in depth of 24 m in dry and 22 m in the wet condition. There is a change in the decreasing percentage because of difference in soil moisture at depth intervals.
Table 5.7: Amplitude in dry and wet condition at location 6 Depth (m)
Amplitude, unit Dry condition
Wet condition
Decreasing %
2
1.71
0.46
73.09
4
0.70
0.36
48.5
6
0.45
0.30
33.33
8
0.16
0.13
18.7
10
0.10
0.10
0
12
0.09
0.08
11.1
14
0.08
0.05
37.5
16
0.06
0.04
33.3
18
0.05
0.02
60
20
0.04
0.01
75
22
0.03
0
100
24
0.03
0
100 Average=49.2 %
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Chapter Five
0
The Effect of Soil Moisture on Radar Signals
0.5
Amplitude, unit 1
1.5
2
2 4 6 8
10
Depth (m)
12
Dry condition Wet condition
14 16 18 20 22
24 26
Figure 5.14: Amplitude in dry and wet condition in different depths at location 6
This part of the study includes difference in the signal amplitudes between the dry and wet conditions, because saturated soils are increasing of the electrical conductivity and attenuating of the signals. Amplitudes are recorded in both conditions and higher signal amplitudes are recorded in the dry condition than in wet in the whole studied locations. The decreasing in amplitude from dry to the wet condition is recorded in any depth and then averaged equal to 56.2 %. This decreasing percentage may differ according to the soil types and water holding capacity of the investigated soils. 91
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5.4 Spectra Analysis The Spectrum of the radar signals of each location in dry and wet conditions are analyzed. It is observed that the high amplitude percentage is in the dry condition. Amplitude percentage has been taken in the same frequency for both cases near the center frequency equal to 100 MHZ. There is a difference in the maximum amplitude between dry and wet condition, as shown in table 5.8 and decreasing percentage is determined. In location 1, the spectrum is analyzed, and it showed there is a great difference between dry and wet condition. At the frequency of 100 MHZ the amplitude percentage is % 100 in dry and % 80 in the wet case as shown in figure (5.15), and the deceasing percentage from dry to wet condition is equal to 20 %.
Figure 5.15: Spectra analysis in dry and wet conditions at location 1 92
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In location 2, the spectra is analyzed and the high amplitude percentage is in the dry condition. At the frequency of 100 MHZ, the amplitude percentage is % 100 in the dry and % 95 in the wet condition as shwon in figure 5.16. The decreasing percentage from dry to wet condition is equal to 5 %.
Figure 5.16: Spectra analysis in dry and wet condition at location 2 93
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The Effect of Soil Moisture on Radar Signals
In location 3, spectra is also analyzed, the high amplitude percentage is recorded in the dry than in the wet condition. At the frequency of 100 MHZ, the amplitude percentage is 88 % in the dry and 67 % in the wet case as shown in figure 5.17. The decreasing in amplitude from dry to wet is 21 %.
Figure 5.17: Spectra analysis in dry and wet condition at location 3 94
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In location 4, the same analysis has been done, and the high amplitude percentage appeared in the dry condition. At the frequency of 100 MHZ, the amplitude percentage is 100 % in the dry and 87 % in the wet case as shown in figure 5.18. The decreasing percentages form dry to wet condition is equal to 13 %.
Figure 5.18: Spectra analysis in dry and wet condition at location 4 95
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The Effect of Soil Moisture on Radar Signals
In location 5, spectra are analyzed, and the high amplitude percentage appeared in the dry as in the wet condition. At the frequency of 100 MHZ, the amplitude percentage is 95 % in the dry and 85 % in the wet condition as shown in figure 5.19. The decreasing in amplitude is equal to 10 % from dry to the wet condition.
Figure 5.19: Spectra analysis in dry and wet condition at location 5 96
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In the location 6, spectra is analyzed as in the other locations, and the high amplitude percentage is noted in the dry condition. At the frequency of 100 MHZ the amplitude percentage is 100 % in the dry and 75 % in the wet case as shown in figure 5.20. The amplitude decreasing from dry to wet is equal to 25 %.
Figure 5.20: Spectra analysis in dry and wet condition at location 6 97
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Table 5.8: Maximum amplitude in dry and wet condition and their difference Locations
Maximum amplitude % Dry
Wet
Decreasing %
Soil type
1
100
80
20
Clay
2
100
95
5
Sandy clay
3
88
67
21
Medium loam
4
100
87
13
Sandy clay loam
5
95
85
10
Loamy sand
6
100
75
25
Sandy loam
From this part of the study, there is an attempt for investigating the effect of soil moisture on the radar depth of penetration and the signal amplitudes through studying the amplitude spectra. The radar sections are obtained in dry and wet conditions, after processing them the spectra is obtained through which the amplitude of the signals are obtained. The maximum amplitude in dry and wet conditions obtained appeared that the higher amplitude is in the dry condition. Decreasing in the max. Amplitude changed from a location to other that may refer to the amount of the moisture and water holding capacity of the soils. The soil moisture may refer to the soil texture that effect the signal amplitudes.
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Chapter Six The Effect of the Soil Composition on the Radar Signals
F
Chapter Six
The Effect of the Soil Composition on the Radar Signals
6.1 Preface Knowledge of soils and soil properties is useful, and often essential, both in the design and operation of GPR surveys. Soils are three dimensional, natural bodies consisting of unconsolidated mineral and organic materials that form a continuous blanket over most of the earth’s land surface. At all scales of measurements, soils are exceedingly complex and variable in biological, chemical, physical, mineralogical, and electromagnetic properties. These properties influence the propagation velocity, attenuation, penetration depth of electromagnetic energy, and the effectiveness of ground penetrating radar (GPR). The effect of soil composition on ground penetrating radar signals is very important because it consists of different components that effect on the radar signals. Generally, soils consist of minerals, organic matter, air and water in pore spaces, as shown in figure 6.1. Each of these components has their effects on the signals caused by different dielectric permittivity (Doolittle et al, 2007). In soils, the most significant conduction based energy losses are due to ionic charge transport in the soil solution and electrochemical processes associated with cations on clay minerals. These losses can seriously impact the performance of GPR. The resolution and penetration depth of GPR are determined by antenna frequency and the electrical properties of earthen materials. Because of high rates of signal attenuation, penetration depths are greatly reduced in soils that have high electrical conductivity and the electrical conductivity of soils increases with increasing water, soluble salt, and /or clay contents (Jol, 2009). Soils around Sulaimani are different from one location to another in their mineralogical composition and textural pattern that may have relation to the geological formations that derive from it (Merza and Mohyaldin, 2005). In this chapter the three parameters that have effect on the radar signals are described. The parameters are mineralogy, chemical composition and soil texture. The soil samples were analyzed to the clay and non-clay minerals by X-ray diffraction, several minerals that have relation to the GPR signals are determined. The soil samples were also analyzed to their chemical composition for several elements such as Na, Ca, K, and Mg, from which soil sodicity and sodium absorption ratio are determined. The texture of each sample is analyzed for their clay, sand and silt percentage. This part is depending on data collected in October, 2013 (Dry condition).
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50 45 40 35 %
30 25 20 15 10 5 0 Mineral particle
Pore space
Organic matter
Soil composition
Figure 6.1: Showing a sample of the soil components (Google search)
6.2 Calculated parameters In this chapter, the calculated parameters that are used in the comparison between the studied locations are mineral composition, chemical composition and soil texture.
6.2.1 The Effect of the Mineral Composition on the Radar Signals Soils contain various proportions of different clay minerals e.g., members of kaolin, mica, chlorite, vermiculite and smectite groups. The size, surface area, cation-exchange capacity (CEC), and water-holding capacity of clay minerals vary greatly. Variations in electrical conductivity are attributed to differences in CEC associated with different clay minerals.
Electrical conductivity and energy loss increase with increasing CEC (Doolittle
et al, 2007). Soils with clay fractions dominated by high CEC clays e.g., Montmorillonite and vermiculitic soil mineralogy classes are more attenuating to GPR than soils with an equivalent percentage of low CEC clays e.g., kaolinitic, gibbsitic, and halloysitic soil mineralogy classes. Soils classified as belonging to the kaolinitic, gibbsitic, and halloysitic mineralogy classes characteristically have low CEC and low base saturation. Calcareous and gypsiferous soils mostly occur in base rich, alkaline environments in semiarid and arid regions. These soils are characterized by layers with secondary accumulations of Calcium 100
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carbonate and calcium sulfate, respectively. High concentrations of calcium carbonate and /or calcium sulfate imply less intense leaching, prevalence of other soluble salts, greater quantities of inherited minerals from parent rock, and accumulations of specific mineral products of weathering. Typically, soils with higher calcium carbonate contents have higher dielectric permittivity (Jol. M. H, 2009). Grant and Schultz (1994) in Jol, 2009 observed a reduction in the depth of GPR penetration in soils that have high concentrations of calcium carbonate. Soils around Sulaimani contain different amount of clay minerals as Montmorillonite, kaolinite and Illite, also non-clay minerals as Calcite and Quartz...etc. (Merza and Mohyaldin, 2005). In the current study soil samples are analyzed again for their mineralogical content, as a result different amount of clay and non-clay minerals were determined such as Montmorillonite, Kaolinite, Illite, calcite and quartz. In the later sections effect of those minerals on the radar signals are determined in detail. Mineral analysis are shown in table 6.1 and figure 6.2.
Location 1 Soil samples were analyzed to the clay and non-clay minerals, and several minerals have been detected that have great effect on the radar signals, as shown in the table 6.1. High percentage of calcite and kaolinite were determined to be suitable with the radar signals, while Montmorillonite that has great effect on the signals is equal to 15.9 %, because of low percent of Montmorillonite, high kaolinite and calcite, the signal attenuation of 0.05 unit/m is recorded as shown in table 6.1, for that finally the radar section performance is fair in this location, as shown in figure 4.3. The maximum amplitude in this location is equal to 100 %, as shown in figure 5.15. The depth of penetration is 25 m. Signal amplitudes are nearly good, as shown in figure 4.20.
Location 2 In this location high percent of kaolinite, Illite, gypsum and calcite were detected that are suitable with the radar signals while low rate of Montmorillonite is determined to have a great effect on the signals, as shown in table 6.1. As a result, a good performance of radar section was obtained, as shown in figure 4.6, then high amplitude percentage is recorded equal to 100 %, as shown in figure 5.16 and attenuation is equal to 0.02 unit/m as shown in table 6.1. The depth of penetration is reached to maximum in comparison to other locations 101
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that equal to 32 m. Signal amplitudes are very good, as shown in figure 4.21.
Location 3 High percent of Montmorillonite has been detected that have a great effect on the radar signals, while low kaolinite and Illite are suitable with the signals in comparison to the Montmorillonite. Low percent of calcite and high quartz percentage were determined in comparison to the locations 1 and 2, as shown in the table 6.1. Because of high percent of Montmorillonite, a fair performance radar section is obtained, as shown in figure 4.9 with 24 m depth, and amplitude decreased to the 88 % in relation to the first and the second location, as shown in figure 5.17. The signal attenuation is also increased in comparison to the second location equal to 0.09 unit/m as shown in table 6.1. Signal amplitudes are weak, as shown in figure 4.22.
Location 4 The soil composition of this location consists of high percent of Illite, kaolinite, calcite and quartz that are suitable with the radar signals. Low percent of Montmorillonite is recorded that it is unsuitable with the signals and attenuating them, as shown in the table 6.1. The performance of the radar section was nearly good because of low percent of Montmorillonite, as shown in figure 4.12 and maximum amplitude of 100 % is recorded, as shown in figure 5.18, with signal attenuation of 0.04 unit/m (table, 6.1). The depth of penetration is 23.5 m. Signal amplitudes are good, as shown in figure 4.23.
Location 5 The effective mineral on the radar signals at this location is the high percent of the Montmorillonite equal to the 33.4 %. A good performance of the radar section was obtained, as shown in figure 4.15 which may refer to the high percent of the calcite. The maximum amplitude doesn’t reach to 100 %, it is equal to 95 %, as shown in figure 5.19. The non-effective minerals as Illite, kaolinite, and quartz have low percent but calcite is high, as shown in table 6.1. The signal amplitude attenuation of 0.02 unit/m is recorded as shown in table 6.1. The depth of penetration of 22.5 m is recorded. Signal amplitudes are good, as shown in figure 4.24.
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Location 6 In this location, because of high percent of Montmorillonite equal to 42.8 % and low percent of kaolinite and calcite with high percent of quartz, as shown in table 6.1, a fair radar section was obtained, as shown in figure 4.18. The maximum amplitude percent is equal to 100 %, as shown in figure 5.20 with the radar signal attenuation equal to 0.02 unit/m, as shown in table 6.1 that may refer to the high percentage of Montmorillonite that has a great effect on the signal amplitudes. The depth of penetration was 23 m in this location. Signals amplitudes are good, as shown in figure 4.25.
Location 7 The maximum percentage of Montmorillonite that is more effective on the radar signals was recorded in the soil of this location that equals 48.3 %, as shown in table 6.1, for that the radar section nearly has a fairly performance, while maximum amplitude percentage is equal to 79 %. The attenuation is reached to the maximum that equals to 0.18 unit/m (table, 6.1), in comparison to the previous locations. The non-effective minerals have low percent as Illite, kaolinite and quartz with high calcite percent. Signal amplitudes are weak, as shown in figure 4.26.
100% 90% Mineral percentage
80% 70%
Quartz
60%
Calcite
50%
Gypsum
40%
Kaolinite
30%
Illite
20%
Montmorillonite
10% 0% 1
2
3
4
5
6
7
Locations
Figure 6.2: Shows minerals percentage at the studied locations 103
Chapter Six
The Effect of the Soil Composition on the Radar Signals
Generally as a result of the mineralogical composition effect on the radar signals, different amount of the clay and non-clay minerals were determined. Maximum amplitude attenuation observed in high percent of Montmorillonite and calcite and minimum amplitude attenuation recoded in high percentage of kaolinite, gypsum, quartz and Illite as in location two.
104
Chapter Six
The Effect of the Soil Composition on the Radar Signals Table (6.1) Shows mineral composition and Ground Penetrating Radar
Locations
Montmorillonite
Illite
Kaolinite
Gypsum
Calcite
Quartz
Depth of
Max.
Signal attenuation
%
%
%
%
%
%
Penetration (m)
amplitude %
Unit/m
1
15.5
3.4
30.6
0
34.4
15.5
25
100
0.05
2
11.6
14.2
24.05
6.01
33
10.7
32
100
0.02
3
40.9
6.7
2.2
0
26.9
22.8
25
88
0.09
4
13.8
10.7
25.4
0
19.6
30.1
23.5
100
0.04
5
33.4
0.05
16.3
0
34.04
16.2
22.5
95
0.02
6
42.8
0
7.1
0
19.08
30.7
23
100
0.02
7
48.3
0.15
1.5
0
43.4
6.3
22.5
79
0.18
105
Chapter Six
The Effect of the Soil Composition on the Radar Signals
6.2.2 Chemical Composition Effect on the Radar Signals Electrical conductivity is directly related to the concentration of dissolved salts in the soil solution, as well as to the type of exchangeable cations and the degree of dissociation of the salts on soil particles. The concentration of salts in the soil solution depends on the degree of water filled porosity, the soil texture, and the minerals found in soils. These salts, together with capillary retained water, produce high attenuation losses that restrict the radar's penetration depths. Because of their high electrical conductivity, saline (saturated extract electrical conductivity ≥ 4 mmhos cm−1) and sodic (sodium absorption ratio ≥ 13) soils are considered unsuited to GPR (Jol, 2009). Soils around Sulaimani contain different concentration of the dissolved salts (Karim, 2007). Samples are analyzed for their chemical composition for determination of the Na, Ca, Mg and K. Chemical data showed by percentage in the analyzed samples, as shown in table (6.2) and figure (6.3) with the GPR data as: attenuation, max. amplitude and depth. Sodium absorption ratios (SAR) are determined that it is a measure of the soil sodicity, as in equation (1) for determination of the soil sodicity, with increasing of the sodicity the suitability to the GPR will decrease (Doolittle et al, 2007). SAR=Na/√1/2(Ca+Mg)……………. (1) (Google search)
Location 1 The soil samples were analyzed chemically to their elements that have relation to the salts in the soils. High content of Ca and low Mg, Na and K are recorded, while Sodium absorption ratio (SAR) is high in comparison to the other locations, as shown in table 6.2. A fair radar section has been obtained, as shown in figure (4.3), the maximum amplitude percentage was equal to 100 %, as shown in figure (5.15), with the signal attenuation is equal to 0.05 unit/m, which may refer to the high SAR. Signal amplitudes are good, as shown in figure 4.20. Radar sections are according to the first traverse.
Location 2 In the current location, low percent of the Na that has a great effect on the soil sodicity (SAR) is low in comparison to the previous location and high Ca with low Mg and K, for that a good performance of radar section was obtained as shown in figure (4.6). The maxi106
Chapter Six
The Effect of the Soil Composition on the Radar Signals
mum signal amplitude reached to the maximum (100 %), as shown in figure (5.16) while signal attenuation 0.02 unit/m was recorded. The sodium absorption ratio was also is low in relation to the first location. Signal amplitudes are very good, as shown in figure 4.21.
Location 3 In this location, in addition to the low Na and sodium absorption ratio with low Mg, K and SAR with high Ca, as shown in table 6.2, a fair performance of the radar section was obtained, as shown in figure (4.9). The maximum signal amplitude did not reach to the 100 %, is equal to the 88 %, as shown in figure (5.17) and may refer to the decreasing of the Ca in comparison to the previous location. The signal attenuation is equal to 0.09 unit/m. Signal amplitudes are weak, as shown in figure 4.22.
Location 4 In this location because of low soil sodicity, low Ca, Mg, Na and high K, as shown in table 6.2, a good radar section performance is obtained, as shown in figure (4.12). The maximum signal amplitude reached maximum that is equal to 100 %, as shown in figure (5.18). Although Ca which suitable with the signals is decreased amplitude reached to the maximum while signal attenuation is 0.04 unit/m. Signal amplitudes are good, as shown in figure 4.23.
Location 5 Although Na and sodium absorption ratio are low in this soil, as shown in table 6.2, as a result a good performance of the radar signals were obtained, as shown in figure 4.15. Maximum amplitude reach maximum, as shown in figure 5.19, and it is high in comparison to the fourth location. High percentage of Ca and Mg were recorded with low K concentration. The signal attenuation for each meter is 0.02 units, that is low in comparison to the first location. This may refer to the low soil sodicity in the soil of this location. Signals amplitude are good, as shown in figure 4.24.
Location 6 The soil type of this location has a low soil sodicity and sodium absorption ratio and low percentage of Ca and K were recorded and high Mg, as shown in table 6.2, for that a fair 107
Chapter Six
The Effect of the Soil Composition on the Radar Signals
performance of the radar section was obtained, as shown in figure 4.18. The radar signal attenuation was equal to 0.02 unit/m, and maximum amplitude is equal to 100 %, as shown in figure (5.20). Signal amplitudes are good, as shown in figure 4.25.
Location 7 In this soil type, the maximum percentage of Ca and Mg were recorded, as shown in table 6.2, in which the maximum signal attenuation recorded is equal to 0.18 unit/m; with a fair performance of the radar section was obtained. The maximum amplitude did not reach maximum and is equal to 79 %. Although Na, soil sodicity and sodium absorption are low, maximum attenuation is recorded. Signal amplitudes are weak, as shown in figure 4.26.
1.4
Element percentage
1.2
1 K
0.8
Na 0.6
Mg
0.4
Ca
0.2 0 1
2
3
4
5
6
7
Locations
Figure 6.3: Chemical composition of the soil samples
The purpose of this analysis is to investigate the effect of the soil chemical composition on the radar signals especially salinity or sodicity of the soils, because with increasing of the salinity suitability of the soil with the GPR will decrease. The soil samples are analyzed chemically for Na, K, Ca and Mg then calculating of the sodium absorption ratio (SAR) from them. Generally, as a result in this section maximum amplitude attenuation observed 108
Chapter Six
The Effect of the Soil Composition on the Radar Signals
in the high concentration of the Ca and Mg and Na, and sodium absorption ratio or soil sodicity as shown in the last location.
109
Chapter Six
The Effect of the Soil Composition on the Radar Signals Table 6.2: Shows element concentrations, SAR, Depth, Max.amplitude and attenuation
Locations
Ca
Mg
Na
K
%
%
%
%
1
0.7
0.08
0.008
0.015
2
0.81
0.06
0.003
3
0.63
0.06
4
0.37
5
SAR
Depth of
Max.
Signal Attenuation
Penetration (m)
Amplitude %
Unit/m
1.43
25
100
0.05
0.015
0.49
32
100
0.02
0.00001
0.015
0.001
24
88
0.09
0.06
0
0.018
0
23.5
100
0.04
0.99
0.05
0.1
0.015
0.001
22.5
95
0.02
6
0.39
0.15
0.1
0.014
0.001
23
100
0.02
7
1.08
0.2
0
0.014
0
22.5
79
0.18
110
Chapter Six
The Effect of the Soil Composition on the Radar Signals
6.2.3 Soil Texture Effect on the Radar Signals Clays and salts provide ions and water facilitates the movement of charges transforming electromagnetic
energy
into
electrical
currents
limiting
the
propagation
of
the
electromagnetic waves. Electrical conductivity in soils is directly related to the amount, distribution, and phase (liquid, solid, or gas) of the soil water, clay and soluble salt contents (Jol,
2009).
Capillary retained
water is sufficient to influence electrical
conductivity even under dry soil moisture conditions. Clays have greater surface areas and can hold more water than the silt and sand fractions at moderate and higher water tensions. Because of their high adsorptive capacity for water and exchangeable cations, clays produce high attenuation losses (Doolittle et al, 2007). Variations in soil texture, topography, crop cover and irrigation practices result in large spatial and temporal variability in soil moisture (Lunt et al, 2004). As a Consequence, the penetration depth of GPR is inversely related to clay content. While clayey (≥35 % clay) soils are restrictive, most sandy (15 % clay) soils are favorable to deep penetration with GPR. Soils around Sulaimani have different texture from one location to another (Aziz and Shareef, 2013). Soil samples are analyzed for their texture to determinate of the clay, sand and silt percentage, as shown in table 6.3 and figure 6.4.
Location 1 The soil texture analysis declared high percentage of clay equal to 41.66 % that has great effect on the radar signals, as shown in table 6.3, and type of the soil was clay. Silt and clay together recorded a high percentage equal to 66.66 %, for that radar section of fair performance was obtained, as shown in figure 4.3. The radar signals reached to the maximum amplitude 100 %, as shown in figure 5.15. The signal attenuation was equal to 0.05 unit/m. Signal amplitudes are good, as shown in figure 4.20.
Location 2 The percentage of clay and clay with silt together decreased in comparison to the first location 51.58 % and sand present that has a minor effect on the radar signals is increased 48.38 %, as shown in table 6.3, with sandy clay type of the soil. A good performance of the radar section, as shown in figure 4.6 while the signal amplitude reached maximum equal to 100 %, as shown in figure 5.16. The signal attenuation recorded the minimum equal to 111
Chapter Six
The Effect of the Soil Composition on the Radar Signals
0.02 unit/m according to the other location. Signal amplitudes are very good, as shown in figure 4.21.
Location 3 The texture analysis recorded low clay percentage, but silt and clay together recorded a high percentage equal to 49.99 %, as shown in table 6.3, and medium loam type soil was recorded. A fair performance of the radar section was obtained, as shown in figure 4.9 and the max.signal amplitude was 88 %, as shown in figure 5.17 and signal attenuation is equal to 0.09 unit/m that it is high in comparison to the previous locations. Signal amplitudes are weak, as shown in figure 4.22.
Location 4 The sand particles recorded a high percentage with low clay and clay silt together, equal to 36.36 % and sand percentage equal to 63.63 %, as shown in table 6.3, with sandy clay loam type soil. As a result good performance of radar section was obtained, as shown in figure 4.12 and maximum amplitude equal to 100 % observed in this location, as shown in figure 5.18, with low attenuation equal to 0.04 unit/m, as shown in table 6.3. Signal amplitudes are good, as shown in figure 4.23.
Location 5 The sand particles recorded the high percentage with low clay and clay silt together equal to 19.63 % and sand percent equal to 80.35, as shown in table 6.3, with loamy sand type of the soil that suitable with GPR survey in dry condition. The signal attenuation was low equal to 0.02 unit/m that refers to that soil texture. Nearly a fair performance of the radar section was obtained, as shown in figure 4.15 and the maximum amplitude percentage was 95 %, as shown in figure 5.19. Signal amplitudes are good, as shown in figure 4.24.
Location 6 High percent of sand equal to 79.45 % with low clay and silt clay together equal to 20.53 % were recorded, as shown in table 6.3, with sandy loam soil type. A nearly fair 112
Chapter Six
The Effect of the Soil Composition on the Radar Signals
performance of the radar section was obtained, as shown in figure 4.18. Low signal attenuation equal to 0.02 unit/m is recorded, while the maximum amplitude percentage equal to 100 % is recorded, as shown in figure 5.20. Signal amplitudes are good, as shown in figure 4.25.
Location 7 The silt clay particles together recorded a high percentage equal to 72.72 %, with low sand percentage equal to 27.27 %, as shown in table 6.3, and clay loam type of the soil was recorded. With the highest percentage of silt clay in the same time highest signal attenuation equals 0.18 unit/m was obtained in the whole studied samples. A fair performance of the radar section is obtained, and the maximum amplitude was equal to 79 %. Signal amplitudes are very weak, as shown in figure 4.26.
100 90 80
Percentage %
70 60 clay
50
silt
40
sand
30 20 10 0 1
2
3
4
5
6
7
Locations
Figure 6.4: Showing the sand, silt and clay % in the soils at studied locations
113
Chapter Six
The Effect of the Soil Composition on the Radar Signals
The purpose of this part of the study is to focus on the effect of the soil textures on the radar signal attenuation because clay soils have a great effect on the radar signals attenuation than the sandy soils. The soil samples are analyzed texturally. Finally, different types of soils are determined such as clay soil, sandy soil, loamy soil, loamy clay soil, loamy sand and sandy loam. These results are studied with the GPR parameters as attenuation of the signals and maximum amplitude. It appeared that the high attenuation and low maximum amplitude are recorded in the high percentage of clay and silt (clay soils)
and
low
attenuation
in
high
percentage
114
of
the
sand
(sandy
soils).
Chapter Six
The Effect of Soil Composition on Radar Signals
Table 6.3: Shows Textural classification of soils and Ground Penetrating Radar data. Locations
Sand
Silt
Clay
Silt+Clay
%
%
%
%
1
33.33
25
41.66
66.66
2
48.33
16.1
35.48
3
50
33.33
4
63.63
5
Soil type
Depth of
Max.
Attenuation
Penetration (m)
Amplitude %
Unit/m
Clay
25
100
0.05
51.58
S.Clay
32
100
0.02
16.66
49.99
M.Loam
24
88
0.09
9.09
27.27
36.36
S.C.Loam
23.5
100
0.04
80.35
8.92
10.71
19.63
L.Sand
22.5
95
0.02
6
79.45
6.84
13.69
20.53
S.Loam
23
100
0.02
7
27.27
36.36
36.36
72.72
C.Loam
22.5
79
0.18
115
Chapter Six
The Effect of the Soil Composition on the Radar Signals
6.3 Soil Attributes and Index Value Several soil attributes for GPR suitability are calculated. Each of the soil attribute is holding an index value according to their suitability from 1-3, as in table (6.4). The index of 1 is good, 2 is fair and 3 is poor for GPR and they are determined with different color for easy calculation. The calculated soil attributes are Sand %, clay %, silt %, Montmorillonite, Illite, Kaolinite, Quartz, Calcite, Gypsum, Ca, K, Na, Mg, K and SAR, as shown in table 6.6. The range of the index value for each soil parameters is depends on the obtained data from the analysis, for example in calculating the index value (IV) for clay, it has effect on the radar signals for that the high percent of clay is holding index value of 3, from 1-30 is holding IV of 1, from 30-60 is holding IV of 2, from 60-100 it is IV of 3, as shown and calculated for all soil parameters in table 6.5. The attribute index value of each sample is calculated by summation of all index value of the current sample. The soil attributes are 14 for that if each attribute is 1, the summation of them is equals 14 in the condition of the good suitability, for that if the index values is more than 1 the attribute index value will increase more than 14 in the condition of the poor or fair for GPR suitability. An example of the attribute index value is calculated for the location one as following:
Sand % (2) + clay % (2) + silt % (1) + Montmorillonite (1) + Illite (3) + Kaolinite (2) + Quartz (3) + Calcite (2) + Gypsum (3) + Na (3) + Ca (1) + Mg (1) + K (1) + SAR (2) = 27
Table 6.4: Index value, GPR suitability and attribute index value Index value
Suitability
Color
Attribute index value
1
Good
14-24
2
Fair
25-34
3
Poor
34 ≤
Minimum attribute index values are in location 2, 4 and 5 that are 24, for that the maximum signal percentage in them are 100 % and low signal attenuation. The soil of location 2, 4 and 5 are located on the Lower Fars, Komitan Formations and Tanjero Formation, leading to GPR survey on them to be suitable. In location 1, the attribute index value is 27 for that the maximum amplitude is 100 % and attenuation of 0.05 unit/m. In 116
Chapter Six
The Effect of the Soil Composition on the Radar Signals
location 3, the attribute index value is also high for that the maximum amplitude in it is 88 % and attenuation of 0.09 unit/m that located on the Shiranish Formation which contains marly limestone. In location 6, the AI is also high, it located on the Red bed Series that contains the reddish shale. In the last location the highest AI is recorded for that the maximum amplitude attenuation is 0.18 unit/m and 79 % of the maximum amplitude.
Table 6.5: Index value of the soil parameters Soil parameters
Index values 1
2
3
Sand %
60-100
30-60
1-30
Clay %
1-30
30-60
60-100
Silt %
1-30
30-60
60-100
Montmorillonite %
1-30
30-60
60-100
Illite %
60-100
30-60
1-30
Kaolinite %
60-100
30-60
1-30
Quartz %
60-100
30-60
1-30
Calcite %
60-100
30-60
1-30
Gypsum %
60-100
30-60
1-30
Na ppm
1-30
30-60
60 ≤
Ca ppm
6000 ≤
3000-6000
1-3000
Mg ppm
1-1000
1000-2000
2000 ≤
K ppm
1-1000
1000-2000
2000 ≤
SAR
Less than 1
1-10
10 ≤
Following the attribute index value calculation for the soils, a map of GPR soil suitability is created depending on the attribute index values that calculated for each location, as shown in figure 6.5. Each soil covered a geological formation and the lithological map shown in the chapter two is used in creating of the soil suitability map.
117
Chapter Six
The Effect of Soil Composition on Radar Signals Table 6.6: Soil attributes for Ground penetrating radar suitability
Location
Clay %
Sand %
Silt %
Montmorillonite %
Kaolinite %
Illite %
Calcite %
Quartz %
Gypsum %
Na/ ppm
Ca/ ppm
Mg / ppm
1
41.66
33.33
25
15.9
30.6
3.4
34.4
15.5
-
89.6
6995
821.5
2
35.48
48.38
16.1
11.6
24.05
14.2
33
10.7
6.05
32.9
8133
683.2
3
16.66
50
33.33
40.9
2.2
6.7
26.9
22.8
-
0.1
6304
605.8
4
27.27
63.63
9.09
13.8
25.4
10.7
19.6
30.1
-
0
3706
637.3
5
10.71
80.35
8.92
33.4
16.3
0.05
33.5
16.2
-
0.1
9941
592.4
6
13.69
79.45
6.84
42.8
7.1
-
19.05
30.7
-
0.1
3942
1540
7
36.36
27.27
36.36
48.3
1.5
0.15
43.4
6.3
-
0
10850
2079
Location
K / ppm
SAR
Attribute index value
Maximum amplitude % 100
Attenuation Unit/m 0.05
GPR Suitability Fair
1
157.1
1.43
27
2 3 4 5
150.8
0.49
24
100
0.02
Good
153.3
0.001
27
88
0.09
Fair
181.5
0
24
100
0.04
Good
158.2
0.001
24
95
0.02
Good
6 7
143.9
0.001
26
100
0.02
Fair
145.9
0
30
79
0.18
Fair
118
Chapter Six
The Effect of Soil Composition on Radar Signals
Figure 6.5: The ground penetrating radar soil suitability map around the Sulaimani City 119
Chapter Seven Results, Conclusions and Recommendations
G
Chapter Seven
Results, Conclusions and Recommendations
7.1 Results and Conclusions The current study evaluated the soils suitability for ground penetrating radar by a number of the soil factor that have effect on the radar signals which include soil thickness, soil moisture, mineralogical composition, chemical composition and soil texture. The following conclusions were obtained:
1-The GPR surveyed on the different soil thickness concluded that the soils have significant effect on the GPR depth of penetration and amplitude attenuation. It is concluded that the radar penetration depth is decreased by 1.2 % for each meter of soil and the radar signal amplitude is decreased by 6.1 % for each meter of the soil. Concluded with increasing of the soil thickness performance of the Ground Penetrating Radar will decrease.
2-The GPR survey was carried out for both dry and wet condition in April and October, 2013. As a result, the soil moisture effect on the penetration depth and amplitude attenuation is calculated. It is concluded that the penetration depth is decreased by 11.06 % from the dry to the wet condition and the radar signal amplitude is decreased by 56.2 %. Concluded that the Ground Penetrating Radar survey is better in the dry condition than in the wet condition.
3-The soil samples were analyzed for their mineralogical composition for clay and nonclay minerals to determinate their effect on the radar signals. It is concluded that the soils rich with clay minerals such as Montmorillonite and non-clay minerals, such as Calcite, have a great effect on the radar signals. Soils that rich with other minerals such as Kaolinite, Illite, Gypsum and Quartz, have a minor effect on the radar signals.
4-The soil samples are analyzed chemically for the Ca, Mg, K, and Na elements concentration as well as determination of the Sodium absorption ratio (SAR). It is concluded that the soils rich with Ca, Mg, Na and SAR, have a great effect on the electromagnetic signals.
120
Chapter Seven
Results, Conclusions and Recommendations
5- The soil samples were analyzed texturally determinate of the ratio of sand, silt and clay effect on the radar signals. Concluded that the soils rich with Clay and silt have great effect on the electromagnetic signals.
6-The GPR survey carried out on the soils that located on different geological formations, among which the soils are derived from Lower Fars, Komitan and Tanjero Formations are more suitable with Ground Penetrating Radar.
7-A ground penetrating radar soil suitability map is created around Sulaimani. Concluded that some soils around Sulaimani City have great effect on the radar signals and some of them have a minor effect.
7.2 Recommendations 1-The soil electrical conductivity has a great effect on the radar signals, for that it is important to carry out an integrate survey by ground penetrating radar and geo-electrical resistivity survey to determinate the soil conductivity and their effect on the radar signals.
2-Determining the amount of the soil moisture so as to determinate the maximum and minimum amount of the soil moisture that has effect on the radar signals.
3-Determining the amount of the large boulders and those particles with in soil profiles that have a size larger than the sand particles, because soils contain different amounts of those particles and have effect on the radar signals.
4- It is recommended that to find the effect of the organic matter, because it has great importance for determining their behavior on the radar signals.
5-Magnetic property of the geological materials has significant effect on the penetrating radar signals. It is important to determinate the soil magnetic property effect on the radar signals
in
future 121
studies.
References
H
References
7.3 References Ali, S.S., Aziz, B.K., Amin, D.A. (2011): Hydrogeology and Geophysical investigation of Ganau lake, Ranya area, Iraqi Kurdistan region, Iraqi Bulletin of Geology and Mining, Vol.8, No.1, 2012, PP 31− 46. Annan, A.P. (2001): Ground Penetrating Radar workshop notes, 1091 Brevik Place Mississauga, Ontario - L4W 3R7 – Canada, 192 P. Aqil, S., and Schmitt, D.R., (2010): Dielectric permittivity of clay adsorbed water: Effect of salinity, GeoCanada 2010 – Working with the Earth, 4 P. Aziz, B.K. (2005): Two dimension resistivity imaging tomography for hydrogeological study in Bazian basin-West Sulaimani City, NE Iraq, University of Sulaimani, 203 P. Aziz, B.K., Ali, S.S. and Karim, K.H. (2012): Geophysical investigation and Geological study of the Delga proposed Dam Site, Qala Diza, Sulaimani City, Kurdistan Region, NEIraq, Journal of Zankoy Sulaimani, 22 P. Aziz, B.Q. and Ali, P.M. (2013): Karst cavity detection in carbonate rocks by integration of high resolution geophysical methods, Journal of Zankoy Sulaimani, 12 P. Bakir, H.B. (2008): Ground Penetrating Radar and Electrical Resistivity Studies for Hamamok Dam Site, NW Koya City, Kurdistan Region, Iraq, College of Engineering, University of Koya, 143 P. Boubaki, N., Saintenoy, A., Tucholka, P. (2011): GPR profiling and electrical resistivity tomography for buried cavity detection: a test site at the Abbaye de l'Ouye (France), Université Paris Sud 11, 5 P. Bristow, C.S., and Jol, H.M. (2003): Ground Penetrating Radar in Sediments, the Geological Society, London, Special Publications, 211, 330 P. Daniels, J.J., (2000): Ground Penetrating Radar Fundamentals, Department of Geological Sciences, The Ohio State University, 21 P. Daniels, D.J. (2004): Ground Penetrating radar, the institutions of electrical engineers, London, United Kingdom, 2nd edition, 734 p. Doolittle, J.A., Minzenmayer, F.E., Waltman, S.W., Benham, E.C., Tuttle, J.W., Peaslee, S.D. (2007): Ground Penetrating radar soil suitability map of the conterminous United States, Geoderma 141, PP 416-421. Dobrin, M.B., and Savit, C.H. (1988): Introduction to geophysical prospecting, Mcgraw. Hil International editions, V. 4, 867 P. 122
References El Qady, G., Hafez, M., Abdalla, M.A., Ushijima, K. (2005): Imaging subsurface cavities using geoelectric tomography and Ground Penetrating Radar, Journal of Cave and Karst Studies, V. 67, No. 3, PP 174–181. Emin, U.U., and İrfan, A. (2006): Detection of cavities in gypsum, Journal of Balkan Geophysical society, Vol. 9, No. 1, December 2006, PP 8-19. Fisher, S.C., Stewart, R.R., and Jolt, H.M. (1992): Processing ground penetrating radar (GPR) data, CREWES Research Report, Volume 4, PP 11-20. Giraldo, M.A. and Gale, S. (2011): Ground penetrating radar (GPR) analysis of soil moisture with in different land uses in an agriculture landscape in Georgia, US, Proceeding of the 2011 Georgia Water Resources Conference, held April 11–13, 2011, at the University of Georgia, 4 P. Gizzi, F.T., Loperte, A., Satriani, A., Lapenna, V., Masini1, N., and Proto, M. (2010): Geo radar investigations to detect cavities in a historical town damaged by an earthquake of the past, Adv. Geosci, 24, PP 15–21. Goodman, D. and Piro, S. (2013): GPR remote sensing in archaeology, Springer, V.9, 233 P. Grote, K., Anger, C., Kelly, B., Hibbard, S., Rubin, Y. (2010): Characterization of Soil Water Content Variability and Soil Texture using GPR Ground wave Techniques, JEEG, September 2010, Volume 15, Issue 3, PP 93–110. Guha, S., Kruse, S. E., Wright, E. E. and Kruse, U. E. (2005): Spectral analysis of ground penetrating radar response to thin sedimentary layers, Geophysical Research Letters, Vol. 32, L23304, 5 P. Hager, J. and Carnevale, M. (2006): The application of low frequency GPR to stratigraphic investigations, Hager GeoScience, Inc. Woburn, Massachusetts, USA, 6 P. Herman, H. (1997): Robotic subsurface mapping using ground penetrating radar, Mellon University, CMU-RI-TR-97-19, 143 P. Jassim, S.Z., and Goff, J.C. (2006): Geology of Iraq, Published by Dolin, Prague and Moravian Museum, Bmo, 2nd edition, 341 P. Jol, H.M. (2009): Ground Penetrating radar theory and applications, Elsevier science, 1 st edition, 524 P. Karim, K.H. (2007): Dynamic of organic matter decomposition and its effect on some micronutrients availability in some sulaimani soils governorate, University of Sulaimani, 123
References 143 P. Lowrie, W. (2007): Fundamentals of Geophysics, Cambridge University Press, New York, second edition, 374 P. Lunt, I.A., Hubbard, S.S, Rubin. Y. (2004): Soil moisture content estimation using ground-penetrating radar reflection data, Journal of Hydrology 307 (2005), PP 254–269. Merza, T.A. and Mohyaldin, I.B. (2005): Manufacture Of Brick Tiles From Local Raw Materials, N & NE Iraq, Journal of Zankoy Sulaimani, part A, PP 30-31. Milan, B.j and Haeni, F.P. (1991): Application of ground penetrating radar methods in hydro geologic studies, Ground water vol 29, no.3, 12 P. Mochales, T., Casas, A.M., Pueyo, E.L., Pueyo, O., Roma´n, M.T., Pocovı, A., Soriano, M.A., Anson, D. (2007): Detection of underground cavities by combining gravity, magnetic and ground penetrating radar surveys: a case study from the Zaragoza area, NE Spain, Environ Geol (2008) 53, PP 1067–1077. Pearce, P.C., Douglas, S., Samuel, K., Noreen, D. (2008): Ground penetrating radar survey at the pyramid complex of Senwosret III at Dahshur, Egypt, 2008: search for the lost boat of a Pharaoh, Journal of Archaeological Science, PP 516-524. Reynolds, J.M., (1997): An Introduction to Applied and Environmental Geophysics, John Wiley & Sons Ltd, Baffins Lane, Chichester,West Sussex POl9 IUD, England, 796 P. Słowik. S. (2012): Influence of measurement conditions on depth range and resolution of GPR images: The example of lowland valley alluvial fill (the Obra River, Poland), Journal of Applied Geophysics 85, PP 1–14. Smith, D.G., jol, H.M. (1995): Ground penetrating radar: antenna frequencies and maximum probable depth of penetration in quaternary sediments, Journal of applied geophysics 33, PP 93-100. Sucre, E.B, Tuttle, J.W., and Fox, T.R. (2011): The use of ground penetrating radar to accurately estimate soil depth in rocky forest soils, Forest science 57 (1), PP 59-66. Takahashi, K., Igel. J., Preetz, H. and Kuroda, S. (2012): Basics and Application of Ground-Penetrating Radar as a Tool for Monitoring Irrigation Process, Leibniz Institute for Applied Geophysics, National Institute for Rural Engineering, Germany, Japan, 27 P. Tekeste, M.Z., Raper, R. and Schwab, E. (2008): Soil Drying Effects on Soil Strength and Depth of Hardpan Layers as Determined from Cone Index Data, Agricultural Engineering International: the CIGR Ejournal, Manuscript LW 07 010. Vol. X. 124
References December 2008, 17 P. Telford, W.M., Geldart, L.P., and Sherif, R.E. (1990): Applied Geophysics, Press syndicate of the University of Cambridge, 2 nd edition, 744 P. Trevor, B., Julia, D., Alice, K. and Renouf, (2005): Application of Ground Penetrating Radar to Mapping Archaeological Features at the Gould Site, Port au Choix, New found land and Labrador studies 20, 1 (2005), PP 0823-1737. Van Dam, R.L. (2001): Causes of ground-penetrating radar reflections in sediment, Vrije Universiteit, Faculty of Earth Sciences, The Netherlands, 110 p. Yehia, E.A., Sherif, M.H., Essam, A.M. and Hany, S.M. (2004): Combined geophysical techniques for cavity detection, EGS Journal, vol. 2, No. 1, PP 147-151. Internet sources: Google search.
125
سهرجۆری له نگاندنیبهكارهێنانی GPR هه ڵسه وروبهریشاریسلێمانی، جیاوازیگڵله ده ههرێمیكوردستانیعێراق.
نامهیهكه پیشكهش كراوه به ئهنجومهنی فاكهڵتی زانست و پهروهرده زانستهكان /زانكۆی سلێمانی /كه بهشێكه له پێداویستیهكانی به دهستهێنانی پلهی ماستهرله زانستی زهویناسی /جیۆفیزیا.
لهالیهن: ڵۆعبدهللاعوسمانسعید هه بهكالۆریۆس /زانكۆی سلێمانی 6002
به سهرپهرشتی: د.بهختیارقادرعزیز پرۆفیسۆر 6102كوزدى
6002شايهى
I
تقييم تطبيق ال GPRعمى أألنواع المختمفة من التربة المحيطة لمدينة السميمانية في اقميم كردستان العراق رسالة مقدمة الى مجمس فاكمتي العموم و تربية العموم سكول العموم في جامعة السميمانية كجزء من متطمبات نيل شهادة ماجستير عموم في عموم األرض /جيوفيزياء. من قبل ىوڵۆ عبداهلل عثمان سعيد بكالوريوس جيولوجي /جامعة السميمانية 2006
باشراف د .بختيار قادر عزيز استاذ
2014ميالدية
1435هجرية
II
ثوختة طووجنانى خؤأل بؤ GPRيةهَطةنطيَهسا هةدةوزوبةزى شازى ضويٌَانى ,يةزيٌَى كوزدضتانى عيَساق .ناوضةى تويَريهةوةكة دةكةويَتة ثشتيَهةى ناجيَطريى تيَلتؤنى ,دةوزةدزاوة بة ييَوَةكانى ثانى ( )3929740.00 N, 3947902.00 Nو ييَوَةكانى دزيَرى ( 2)542059.00 E, 530496.00 Eتويَريهةوةكة ثيَلًاتووة هة كازيطةزى ئةضتووزى خؤيَ ,شىَ ى خؤيَ ,وة ثيَلًاتةى خؤيَ كة ثيَلًاتووة هة كانصاكاى ,خويَلاى هةطةيَ ثيَلًاتةى دةنل ؤهَةكاى هة ضةز شةثؤىل زِادازى .حةوت شويَو يةهَبريَسدزا هةدةوزوبةزى شازى ضويٌَانى كة دةكةونة ضةز جؤزى جياواشى طىَ و ضةز ثيَلًاتةى جيؤهؤجى جياواشى وةن ثيالضجى ,تاجنةزؤ, فازضى خوازوو ,فازضى ضةزوو ,كؤًيتاى ,زِيَدبيَد ,هةطةيَ شريانش. ئاًيَسى GPR / Mala Ramacبةكازييَهسا هة تويَريهةوةكةدا و شانيازى كؤكسدنةوةدا 1 ,ييَىَ ديازى كسا هة يةز شويَهيَم دا هةضةز ئةضتووزى خؤهَى جياواش و دووزى ئاضؤى هة ضيهةكانةوة بة يةًاى زِيصى ثيَلًاتةكانى ئاًيَسى GPRوةن هةزةهةز(355 ًيَطاييَستص) ,كات ,ذًازةى منوونةكاى ,هةزةهةزى منوونةكاى .هةيةز شويَهيَم 1بسِطةى GPRدةضتلةوت و ضاكلساى بة بة كازييَهانى باشرتيو فيوتةز وة طؤزِيهياى هة بسِكةى كاتةوة بؤ بسِطةى قووهَى. يةز ييَوَيَم هةضةز ئةضتووزى خؤهَى جياواش وةزطريا ,ييَوَى يةكةم هةضةز .م ,ييَوَى دووةم هةضةز 8م ,ييَوَى ضيَ يةم هةضةز 3.م كةدؤشزاونةتةوة بةيؤى ديصايهيَلى تايبةت هة كيَوَطةدا بةيازًةتى يةنديَ شانيازى تسى وةن طؤشةى الزى ضيهةكاى .زِووثيَوويةكة ئةجنام دزا هة .وةزشى جياواشدا ,هة ًانطى .و 35ى .531كة تياياندا زِيَرةى شىَ جياواشة ,بؤ دؤشيهةوةى كازيطةزى شيَ هةضةز شةثؤىل زِادازى .هةيةز شويَهيَم منوونةى خؤهَلاى كوكسانةوةو شيلازياى بؤ كسا بؤ ثيَلًاتةى كانصاكاى ,خويَلاى ,ثيَلًاتةى دةنلؤهَةكاى و كازيطةزياى هةضةز شةثؤىل زِادازى. كازيطةزى ئةضتووزى خؤيَ ديازى كس ا هةضةز شةثؤىل زِادازى ,دةزكةوت كة قووهَى زِادازى كةم دةكات بةزِيَرةى 32. %بؤ يةز ًةتسيَم هة خؤيَ ,وة بةزشى شةثؤي كةم دةكات بةزِيرةى .23 %بؤ يةز ًةتسيَم هة خؤيَ .كازيطةزى شيَ ى خؤيَ ديازى كسا هةضةز شةثؤىل زِادازى ,دةزكةوت كة قووهَى زِادازى كةم دةكات بة زِيَرةى 332. %هة ووشلةوة بؤ شيَ ى شؤز ,وة يةزوةيا بةزشى شةثؤي كةم دةكات بة زِيَرةى 0.2. %هة ووشلةوة بؤ شيَ ى شؤز. كازيطةزى ثيَلًاتةى خؤيَ ديازى كسا هةضةز شةثؤىل زِادازى ,كة بسيتى ية هة ثيَلًاتةى كانصاكاى ,خويَلاى ,هةطةيَ ثيَلًاتةى دةنلؤهَةى .دةزكةوت بةزشتسيو وونبوونى بةزشى شةثؤي هة بةزشتسيو زِيَرةى Montmorilloniteو Calciteوة كةًرتيو وونبووى هةبةزشتسيو زِيَرةى Kaolinite, Gypsum, Illiteو .Quartz منوونةى خؤهَةكاى شيلازى كيٌياياى بؤكسا بؤ Ca, K, Mgوة , Naدةزكةوت كة بةزشتسيو وونبوونى بةزشى شةثؤي هة بةزشتسيو زِيَرةى Ca, Mgوة Naدا ديازى كسا .منوونةى خؤهَلاى شيلازياى بو كسا بؤ ثيَلًاتةى دةنلؤهَةى كة بسييت ية Sand,
III
siltوة Clayو كازيطةزياى هةضةز شةثؤىل زِادازى .دةزكةوت كة بةزشتسيو وونبوونى بةزشى شةثؤىل هة بةزشتسيو زِيَرةى Siltو Clayداية وة كةًرتيو وونبووى هة شؤزتسيو زِيَرةى Sandداية .ئةم زِووثيَووية زِادازى ية هةضةز جؤزى جياواشى خؤيَ كساوة كة ئةوانيش دةكةونة ضةز ثيَلًاتةى جيؤهؤجى جياواش ,دةزكةوت كة ئةو خؤهَانةى دةكةونة ضةز ثيَلًاتةى فازضى خوازوو ,كؤًيتاى وتاجنةزؤ باشرتى وةن هة خؤهَةكانى تس ,هةكؤتاى دا نةخشةى طووجنانى خؤيَ بؤ GPRدزووضتلسا هةدةووزوبةزى شازى ضويٌَانى.
IV
المستخمص تم تقيم انسجام التربة لمسح ال GPRفي ضواحي مدينة السميمانية في اقميم كردستان العراق .تكتونيا تقع منطقة الدراسة ضمن نطاق غير مستقرة حسب الخارطة البنيوية لمعراق بين خطي عرض (3929740.00 و 3947902.00شماال ) وخطي طول ( 542059.00و 530496.00شرقا) .تضمنت الدراسة تاثير سمك ورطوبة ومكونات التربة من المعادن والمموحة و نسيج التربة عمى موجات الرادار .تم اختيار سبعة مواقع من ضواحى مدينة السميمانية تق ع عمى تربة لتكوينات جيولوجية مختمفة مثل البيالسبي وتانجرو وكوميتان و شرانش و وسمسة الطبقات الحمراء و الفتحة . استخدم
جياز ال GPRلمفحوصات و عممية جمع المعمومات .تم تحديد ثالثة خطوط مسح بطول 45متر لكل
خط وعمى سماكات مختمفة لمتربة ومن مسافات افقية مختم فة لممكشف الصخري .تم اخذ القياسات بشكل موحد لجميع المواقع من حيث تثبيت معامالت الجياز كذبذبة الموجات ( )055ميغاىرتز ,ونافذة الوقت وفترة التوقف وعدد النماذج وذبذبة النماذج .تم تسجيل المقاطع الرادارية وتمت معالجتيا باستعمال مرشحات مناسبة لتغييرىا من مقاطع وقتية الى مقاطع عمقية. الخط األول من كل مقطع تم تنفيذه عمى سمك تربة 3امتار والخط الثاني عمى سمك 8امتار والثالث عمى سمك 01متر .تم تحديد ىذه السماكات وفق تصاميم خاصة في الحقل بأألضافة الى معمومات حقمية اخرى كميل الطبقات .اجري المسح في موسمين مختمفتين .ألشير الرايع والشير العاشر من عام 1502والتي تكون فييما نسبة الرطوبة مختمفة لتحديد تاثير الرطوبة عمى موجات الرادار وقابمية اختراقيا .تم تحميل نمازج التربة في كل مواقع الدراسة من حيث مكوناتيا المعدنية و المموحة ,و نسيج التربة وتاثيرىم عمى موجات الرادار. تم حساب تاثير سمك التربة عمى موجات الرادار و تبين بان عمق االختراق ينقص بنسبة % 1.2لكل متر من التربة و مدى التردد ينقص بنسبة % 5.0لكل متر من التربة. تمت دراسة تاثير الرطوبة عمى موجات الرادار و تبين بان عمق االختراق ينقص بنسبة % 00.5من الجفاف الى الرطوبة و مدى التردد ينقص بنسبة % 45.1من الجفاف الى الرطوبة. تم تحديد تاثير مكونات التربة المعدنية والكيمياوية والنسيجية عمى موجات الرادار وتبين بأن اعمى نسبة توىين في مدى التردد كانت مع ارتفاع نسبة معدني المنتورولونايت والكالسايت واقل نسبة توىين سج مت كانت بأرتفاع نسب معدن الكوارتز والكاولين و الجبس واألاليت. التحميل الكيمياوي لمتربة اجري لحساب نسبة المعادن الوافرة مثل Caو Naو Kو Mgولوحظ بان اعمى توىين لمدى التردد كان عند ارتفاع نسب تركيز ال
Naو Caو Mgوارتفاع نسبة امتصاص الصوديوم .
تم تحميل النماذج ايضا من ناحية محتواىا من أألنسجة الرممية والسمتية والطينية وتاثيرىا عمى موجات الرادار وتبين بان اعمى توىين لمدى التردد لجميع النماذج المدروسة كان مع ارتفاع نسب السمت والطين وأدنى توىين كان مع انخفاض نسب السمت والطين وارتفاع نسبة حبيبات الرمل.
V
وتبين من خالل ىذه الدراسة بأن التربة الواقعة فوق تكوينات الفتحة والكوميتان والتانجيرو اكثر مالئمة لمسح GPRمن التربة الواقعة عمى التكاوين أألخرى. تم رسم خارطة تبين مدى مالئمة التربة الواقعة في ضواحي مدينة السميمانية لمسح ال .GPR
VI
