Environ Earth Sci DOI 10.1007/s12665-010-0791-0

ORIGINAL ARTICLE

Effects of monsoonal rainfall on waste dump stability and respective geo-environmental issues: a case study Mohan Yellishetty • William J. Darlington

Received: 5 January 2010 / Accepted: 5 October 2010 Ó Springer-Verlag 2010

Abstract The stability of mine waste dumps is of critical importance and an issue, the mining industry of Goa, India is continually facing. The State of Goa receives high rainfall of around 3,000 mm annually. This heavy monsoonal rainfall is often believed to be the cause of dump slope instability. In light of several dump collapses encountered in the State and their damaging effects on both mine operations and local geo-environmental conditions, this paper examines their stability considering various geotechnical factors and the downstream environmental effects of a slope failure. The mechanical properties of dump waste material are reported at different compaction levels. The effect of these properties and changes in porewater pressure are specifically examined using limit equilibrium analysis. An empirical formula is developed relating dump height, material mechanical parameters and pore-water pressure to the factor of safety of the slope. It was found that the level of compaction experienced by the material had a significant effect on the factor of safety.

dumps. Active iron-ore mining operations currently cover 5% of Goa (or approximately 18,300 ha) (Chaulya et al. 1999). Throughout India, iron-ore is predominantly mined using open cut mining methods. The present iron-ore mining rate of 16–21 million tonne per annum coupled with high ore-overburden ratios of around 1:3 results in a need to remove and dispose of 40–50 million m3 of waste per year. The waste dumps generated by this level of disposal often comprise of not only overburden material, but sometimes processed tailings. The development and management of such facilities can pose major problems in terms of mine operations and later, the mine reclamation. This paper presents a detailed geotechnical investigation of the stability of mine waste dumps and a review of the relevant geo-environmental issues considering high rainfall effects. By obtaining actual site data, it has been possible to perform a limit-equilibrium slope stability study of a mine waste dump. This study has quantified the effect of various soil properties and an increase in pore pressures due to heavy rainfall on waste dump stability.

Keywords Iron-ore mining  Waste dump  Water table  Slope stability  Factor of safety Literature review Introduction

Waste dump instability: a geotechnical perspective

Large scale open cut mining operations have resulted in a significant increase in the volume and size of steep waste

The instability of large waste dumps can result in both operational and environmental problems. Due to increased environmental awareness and the risks to personnel and equipment, mine operators are now making efforts to address both short-term and long-term concerns. Robertson (1986) has ascertained that the long-term stability of waste dump slopes can decrease as a result of (i) increases in the groundwater table (due to groundwater accumulation and changes in the permeability of the dump

Part of the work was undertaken when at CESE, IIT Bombay, Powai, Mumbai 400076. M. Yellishetty (&)  W. J. Darlington Department of Civil Engineering, Monash University, Clayton, VIC 3800, Australia e-mail: [email protected]

123

Environ Earth Sci

materials resulting from weathering and the in-washing of fines), and (ii) decreases in the dump material strength (due to weathering). Robertson’s general findings were supported by the Indian Bureau of Mines (IBM 1995) wherein it was reported that inadequate drainage increases the phreatic surface ultimately resulting in decreased shear strength of the underlying material. Furthermore the IBM (1995) reported that improper compaction decreases shear strength, increases permeability, and increases excessive consolidation; with differential settlement eventually leading to failure of embankments. Caldwell and Moss (1981) proposed (i) limiting the height of dumps, (ii) flattening slopes, (iii) avoiding weak foundations at the toe of the dump, and (iv) preventing pore pressure build-up through drainage as a means to ensure long-term slope stability. The idea of rainfall infiltration of a slope has been explored by several researchers. Through three-dimensional numerical modelling the effect of various rainfall patterns on the groundwater response of an unsaturated slope has been explored (Ng et al. 2001). Prolonged rainfall with high rain volume produced the greatest change in pore-water pressure and it was noted that high intensity did not necessarily produce a dramatic increase in pore-water pressure (here surface permeability prevented complete infiltration resulting in significant run-off). The general findings of this research are supported by Gavin and Xue (2008); and Xue and Gavin (2008) who assessed the rainfall infiltration into unsaturated and partially saturated slopes, respectively. Their findings indicated that not only will the rainfall intensity and duration control infiltration, but also the rainfall pattern. Greater infiltration was seen when rainfall was initially of high intensity and later of low intensity (as opposed to events that commenced with low intensity and concluded with high intensity). Cho and Lee (2001, 2002) considered not only infiltration characteristics, but also the resulting stability of a slope due to rainfall. Their research concentrated on shallow failures induced by infiltrating rainwater which created zones of reduced matric suction and thus reduced shear strength. However, this paper will consider deep-seated failure resulting from long rainfall durations with high intensities (monsoonal rains). Under these circumstances Ng et al. (2001) has shown that even after rainfall has ceased the hydraulic head at depth will continue to rise thereby increasing the probability of deep-seated failures. Waste dump instability: a geo-environmental perspective Mine waste containment and dump stabilisation are vital for successful mine site rehabilitation. The recent geochemical research studies conducted on mine waste from Goa by Yellishetty (2004); Kumar et al. (2003); Juwarkar

123

et al. (2003) and IBM (2002) emphasise this need for the mining industry of Goa. Juwarkar et al. (2003) performed chemical analysis on mine waste typical of the area; these findings are presented in Table 1. The high heavy metal content of the waste material is of key importance when considering the environmental impact of a waste dump slope failure. Further mineralogical studies by Kumar et al. (2003) suggest that ore commonly found in the State of Goa comprises of hematite, magnetite, limonite, and goethite. Further petrographical studies conducted by them identified additional ore mineral phases not listed above including; pyrrhotite, platinum bearing minerals (e.g., marcasite and magnemite), and gold bearing arsenopyrite. These sulfide minerals have potential acid-producing characteristics. In general, the pyrite oxidation depends upon: surface area of pyrite, form of pyretic sulfur, oxygen concentration, solution pH, catalytic agents, flushing frequencies, and the presence of Thiobacillus bacteria (Caruccio et al. 1998; Smith and Shumate 1970). IBM (2002) reports that agricultural fields, irrigation canals, river beds and creeks are prone to heavy siltation and sediment deposition in Goa. This is due to the heavy in-wash from mine dumps occurring annually after periods of heavy rainfall. It was reported by IBM (2002) and Juwarkar et al. (2003) that mine waste is deprived of plant Table 1 Physico-chemical characteristics of mine waste from Goa Physical properties of soil (Juwarkar et al. 2003) Maximum water holding capacity (%)

35.5–37.6

Porosity (%)

32.5–40.7

Chemical properties of the soil (Juwarkar et al. 2003) pH 6.0–6.5 EC (mS/cm)

0.44–0.55

Na (mq/l)

0.01–0.03

K (mq/l)

0.007–0.009

Heavy metals (ppm)

Juwarkar et al. (2003)

Yellishetty et al. (2009)

Cr

130–300

166–171

Zn

300–600

93–99

Pb

60–150

49–56

Cd

6–20

15–21

Ni

200–250

38–48

Mn

9,860–12,490

24,990–25,015

Fe

108,400–123,430

369,247–369,375

Cu

80–150

64–68

Nutrients (Juwarkar et al. 2003) Organic carbon (%)

0.14–0.16

Nitrogen (%)

0.003–0.007

Phosphorus (%)

0.003–0.009

Potash (%)

0.005–0.010

Environ Earth Sci

average rainfall varies between 3,000 and 4,000 mm with highest rainfall occurring in July while the lowest rainfall occurs in February.

supporting nutrients, hence posing a great threat to agricultural yields and fish populations. Yellishetty et al. (2008) has shown the potential of using this waste in civil engineering construction as an alternative to the predominantly granite and laterite aggregates currently utilised in construction materials.

Materials and methods Soil sampling and testing

Location, geology and climate of the study area Overburden samples were collected from the six waste dumps marked in Fig. 1. In collecting these samples, the procedures recommended by Sobek et al. (1978) and ASTM D4220 (ASTM 2007a) were followed. Each representative sample weighed 3 kg. Care was taken to retain the soil moisture content by sealing the samples in plastic bags. Later, an array of laboratory experiments was performed on each sample (Table 2). Cylindrical specimens with a diameter of 38 mm and height twice the diameter were used in the triaxial testing.

Samples used in testing were obtained from Sesa Goa Limited’s Codli Mine, Goa. The landmass of Goa is a rising plateau between longitude 14°480 0000 and 15°480 0000 and latitude 73°400 0000 and 74°200 0700 with an area of approximately 3,700 km2 and a coastline extending over 100 km (Fig. 1). Goa produces large quantities of iron and manganese ore, while bauxite and silica sand are also extracted. The iron-ore formation of Goa is considered to be the northern most extension of the Shimoga-North Kanara-Goa supracrustal belt of the Dharwad super group area and forms the western part of the castle rock schist belt. The principal iron-ore ranges of Goa are: (1) Bicholim–Pale range, (2) Conquirem–Poikul–Melca range passing through Sacorda, (3) Shigao–Kaley–Tathodi range, (4) Kirlapal–Codli–Costi range, (5) Tudou–Barazan–Uguem range, and (6) Pirla– Sulcorna range. The current study area of Codli is located in Sanguem Taluka, South-Goa district, Goa (Fig. 1). The study area receives rainfall from southwest monsoons between the months of June and September. The

ara

sht

ra North 10

5

0

20 km

10

DW7

Working Pit

Kha n

IC

Rive r

DW6

H O LI

Pit 3 Working Pit

SATTARI

M

Dump 6

Valpoi

Pit 4

n bia Ara

Panaji 2000N

Sacorda

Vasco

Dump 1 Pit 6

Pit 8 Water reservoir

a Se

Ponda

Curchorem

India S A N G

Goa

U E

Karnataka

Pit 1 Water reservoir

Margao

Pit 5 (Under reclaimation) Pit 7

Offices/w'shops Dump 2

Dump 5 DW2

DW4

Dump 3

M

Iron Ore

DW1

Chaudi

DW3

Bauxite Ore Manganese Ore Codli

5000E

4000E

DW9

DW11

B

Mapusa

3000E

DW8 DW10

dep ar

Mah

To evaluate the effect of ground water on geotechnical stability, the water regime of the study area was observed. Monitoring of the groundwater table was carried out at dug-wells 1–5 (DW 1–5, Fig. 1) where water levels were measured prior to and during the monsoon season for a period of 4 years. The selection of dug-well positions was based on the underlying aquifer location, accessibility and distance from mining operations.

2000E

3000N

Ground water monitoring

Dump 4 1000N Soil collection points (Dumps) Dugwells (DW1-11) Tailings collection points 500 250 0 500 m

No r

Prominent wind direction th

DW5

Fig. 1 Location map and plan of the study area at the time of the study

123

Environ Earth Sci Table 2 List of experiments conducted in the study and relevant standards followed Parameter

Standard description

Reference

Particle size distribution

To calculate the particle size distribution of the waste dump material from the study area

ASTM D4220 (ASTM 2007d)

To calculate the particle-size distribution (gradation) of soils using sieve analysis

ASTM D6913 (ASTM 2004b)

To classify the soils based on unified soil classification system (USCS)

ASTM D2487 (ASTM 2006a)

To measure the field bulk density of the waste dump material in study area

ASTM D2937 (ASTM 2004a)

Bulk density Moisture content

To determine the soil water (moisture) content in laboratory

ASTM D2216 (ASTM 2005)

Optimum moisture content (OMC)

To evaluate the compaction characteristics of soil using modified effort To determine the strength and stress–strain relationships of a cylindrical specimen

ASTM D1557 (ASTM 2007c)

To calculate the specific gravity of soil by water pycnometer

ASTM D854 (ASTM 2006b)

Soil cohesion and friction angle Specific gravity

ASTM D2850 (ASTM 2007b)

Numerical modelling

Table 3 Physical characteristics of the waste dump material from study area

Factor of safety (FOS) analysis was carried out using the limit equilibrium analysis program SLOPE/W (GeoSlope International). The comprehensive formulation of SLOPE/W makes it possible to easily analyse both simple and complex slope stability problems using a variety of methods to calculate the FOS. This study utilised the general limit equilibrium (GLE) theory. GLE solves two FOS equations: one satisfying force equilibrium and the other satisfying moment equilibrium (a more detailed description of these can be found in Krahn 2004). The GLE model incorporated an automatic search routine to calculate the critical slip surface and minimum FOS. It was assumed the dump foundation was horizontal and stable. The waste was modeled as free-draining, but the effect of different phreatic surface levels was also explored to assess the effect of pre-monsoon and monsoon season water table levels. Dump heights of 10, 11, 13, and 15 m were modeled using a slope angle of 33° (equal to the average angle of repose) and material properties corresponding to densities of 1.5 g/cc (i.e., c = 12 kPa, / = 13.82°), 1.92 g/cc (i.e., c = 14 kPa, / = 28.89°), and 2.3 g/cc (i.e., c = 26 kPa, / = 38°).

Parameter

Results and discussion Material properties The soil samples collected from the study area were analysed in the laboratory to obtain their moisture content, specific gravity, bulk-density, maximum dry density and shear strength. These results are reported in Table 3.

123

Value

Moisture content (%)

18.8

Specific gravity

3.49

Field bulk density

1.50–1.65 g/cc

Maximum dry density

2.1 g/cc at 19% moisture (i.e., OMC)

Particle size distributions of the dump material were found for the six samples (Fig. 2). The particle size distribution reported varies greatly from those presented for mines located in other parts of the world (i.e., Davis and Ritchie 1987; Rassam and Williams 1997; Williams 1996). The obvious variability in the particle size distribution between each sample and those presented by other researchers is due mainly to differences in crushing and compaction during extraction and dumping of the waste, and the waste dump material’s initial inherent geological properties. Figure 2 shows that approximately 20% of the material is within the sand–silt–clay range. Often it is believed that the unsaturated clay fraction of mine waste may lead to dump slope instability (Chu et al. 2002) and this may be one of the factors contributing to dump instabilities in Goa at heights that prove stable elsewhere. According to the unified soil classification system (USCS) all the samples collected fall into the SW soil category (well graded sands, gravelly sands, little or no fines) (Table 4). However, the uniformity coefficient varies greatly between samples. Unconsolidated–undrained (U–U) triaxial tests were used to determine the shear strength and cohesion of the waste dump material at the field bulk density (1.5 g/cc). A plot of deviator stress versus axial strain was used to

Environ Earth Sci Fig. 2 Particle size distribution of six samples taken from the Codli Mine waste dumps

100

S1

90

S2 S3

80

S4

% Passing

70

S5 S6

60

Average 50 40 30 20 10

0 0.001

0.01

0.1

1

10

100

Particle diameter (mm)

Table 4 Classification of the Codli Mine waste dump soil in accordance with USCS

Samples

Diameter corresponding to

Uniformity coefficient (Cu)

Coefficient of gradation (Cc)

Soil type and description

SW–well graded sands, gravelly sands, little or no fines

D10

D30

D60

S6

0.0275

0.0675

0.18

6.55

0.92

S5

0.057

0.07

0.525

9.21

0.16

S4

NIL

0.06

5.75

NA

NA

S3

0.05

0.06

0.08

1.60

0.90

S2

0.055

0.12

0.225

4.09

1.16

S1

0.05

0.6

5.5

110.00

1.31

Average

0.06

0.07

0.4

6.67

0.20

compute values of normal stress (Fig. 3). From these results the Mohr’s circle was constructed and the cohesion (c) and angle of internal friction (/) were measured as 12 kPa and 13.82°, respectively for the material’s field bulk density (1.5 g/cc). In order to further understand the consolidation behavior of the dump material and its effects on stability, subsequent U–U triaxial tests were performed on the waste dump material at densities of 1.92, 2.0, and 2.3 g/cc (increased densities were obtained through increased compaction) (Table 5).

on any geotechnical works in the area and is of great concern to mine management with high phreatic surfaces leading to mine slope failures in other areas of Goa. Also of great importance and relevance to this study is the dramatic change between pre-monsoon and monsoon levels, which can vary between 1.25 and 9.1 m. Changes as dramatic and large as these will clearly influence dump slope stability. This paper aims to quantify at what point these changes may lead to slope failure.

Groundwater monitoring

The stability of the waste dump was modeled using GLE methodology for various dump heights and with different ground water conditions. Increases in the ground water level were used to approximate changes that are induced during the monsoon season. Through well monitoring and consideration of the work of Ng et al. (2001) a rise in the water table is inevitable during the monsoon season given the rainfall intensity and duration. Figure 4a shows a typical failure surface for a waste dump from the study area without pore-water pressure, while Fig. 4b shows the effect

The groundwater table in the study area is at 32 m with respect to mean sea level (MSL). The current mining operations have gone below -24 m (MSL). Variations in groundwater depths obtained from observation wells (during pre-monsoon and monsoon seasons of different years) are shown in Table 6. The readings demonstrate how relatively close the water table is to the ground level in the study area. The ground water height bears considerably

Stability analysis of the waste dump from study area

123

Environ Earth Sci

Deviator stress (kPa)

(a) 250 200

100 kPa

Table 5 Relationship between density, cohesion and friction angle of the Codli Mine waste dump material

200 kPa

Density (g/cc)

Cohesion (kPa)

Friction angle (°)

1.5

12

13.8

1.9

14

28.9

2

16

30

2.3

26

38.0

300 kPa 150

100

50

Table 6 Ground water level during pre-monsoon and monsoon seasons

0 0

2

4

6

8

10

Well no. Reduced levels of water column from MSL (m)

% Strain

Deviator Stress (kPa)

(b) 700 100 kPa

600

200 kPa 500

300 kPa

400

Year 2000

Year 2001

Year 2002

Year 2003

PM

PM

PM

PM

M

M

M

M

DW1

33.79 35.84 33.54 36.04 33.69 36.24 31.59 36.39

DW2

27.65 36.75 27.75 35.85 27.80 35.00 28.73 37.45

DW3*

33.30 38.20 33.60 37.70 33.40 37.05 33.33 38.30

300

DW4

25.25 29.40 25.20 28.80 25.20 28.00 25.15 29.60

200

DW5*

36.30 37.80 36.40 37.65 36.35 37.75 36.69 38.45

PM Pre-monsoon, M monsoon

100

* Indicates wells outside the lease area 0 0

2

4

6

8

10

12

14

16

18

% Strain

(c) 1200

Deviator Stress (kPa)

1000

800

600

400 100 kPa 200

200 kPa 300 kPa

0 0

2

4

6

8

10

12

14

16

18

% Strain Fig. 3 a Stress strain curves obtained through triaxial testing on the Codli Mine waste dump material at field bulk density (density = 1.5 g/cc). b Stress strain curves obtained through triaxial testing on the Codli Mine waste dump material with increased density (density = 1.92 g/cc). c Stress strain curves obtained through triaxial testing on the Codli Mine waste dump material with increased density (density = 2.34 g/cc)

of a rise in the water table. The scenarios modeled in this paper only consider the dumps under steady state conditions. The effect of a transient rise in the water table are outside the scope of this paper, although it is known that infiltration of rainwater through an unsaturated zone results

123

in the formation of a wetted zone near the slope surface which may lead to shallow failures during periods of rainfall (Cho and Lee 2002; Fourie et al. 1999; Rahardjo et al. 1994). A complete set of results obtained through a parametric study using SLOPE/W is shown in Fig. 5 which outlines the FOS of different dump heights and PWP conditions. Considering the field bulk density (1.5 g/cc) under nonmonsoon circumstances (without pore pressure), and with a dump height of 13 m the FOS was unity. However, once the dump height exceeds 13 m, the FOS falls below unity (Fig. 5). Furthermore, even if the dump height is reduced to as low as 10 m, it still becomes unsafe if the PWP exceeds 2.9 m, a common event in the area during monsoon season (Table 6). From an operational perspective, given the heavy rainfall experienced in the region and the high sensitivity of the FOS to changes in the phreatic level, active monitoring of PWP in dumps is clearly necessary. The experimental results presented in Table 5 show that the friction angle and cohesive strength of the soil increase with an increase in density as a result of compaction. Further numerical modeling revealed that when the dump was modeled using the cohesion and friction angle associated with the compacted material, the FOS increased dramatically (Fig. 5). In terms of dump management and development, this increased compaction could be generated through the movement of heavy earth moving machinery over the dump. This increased compaction will also aid in

Environ Earth Sci

15 1

3

4

10

20

1.076 12 11 1.082 1.088 1.095 1.088 1.106 1.095 1.141 1.120 1.103 1.132 1.209 1.132 1.138 1.111 1.209 1.366 1.133 1.159 9 1.127 1.136 1.190 1.371 1.711 1.140 1.146 1.188 1.297 1.529 1.186 2.118 1.154 1.188 1.264 1.533 2.110 1.260 1.197 1.250 1.417 1.781 1.427 1.251 1.354 1.782 1.591 1.333 1.599 1.483 10

HEIGHT

HEIGHT

20

15 4

3 1

10

5

0.931 12 11 0.942 0.930 0.950 0.935 0.962 0.939 0.977 0.983 0.947 0.958 1.016 1.008 0.959 0.956 1.024 1.154 1.036 0.970 0.958 0.996 1.172 9 0.966 1.468 0.986 0.972 0.990 1.086 1.276 0.991 0.984 0.994 1.043 1.295 1.048 1.001 1.030 1.171 1.192 1.030 1.109 1.291 1.080 1.315 1.192 10

5

8

8

5

5

6

6 14

13

7

0

2

7 2

1

0

5

10

15

20

25

30

35

40

DISTANCE

0

2

2

1

0

5

10

15

20

25

30

35

40

DISTANCE

Fig. 4 Limit equilibrium failure envelope of a waste dump generated in SLOPE/W: a without PWP and b with PWP

Fig. 5 Results of parametric study completed using SLOPE/W showing the relationship between the dump height and FOS under various PWP conditions [1.5 g/cc bulk density (c = 12 kPa, / = 13.8°); 1.9 g/cc bulk density (c = 14, / = 28.9°); 2.3 g/cc bulk density (c = 16, / = 38°)]

limiting environmental impacts of a waste dump, with an increase in cohesion aiding the prevention of soil erosion and dump collapse (Wu 1995). Based on the results of numerical modeling conducted using SLOPE/W and discussed above the following empirical relationship was developed to predict the FOS of a waste dump (Eq. 1): FOS ¼ 0:027c þ 0:04/  0:033DH  0:083PWP þ 0:65

ð1Þ

where FOS is the factor of safety, c is the cohesion (kPa), / is the angle of internal friction (in degrees), DH is the dump height (m), and PWP is the pore-water pressure (m)

Multiple linear regression analysis of a dataset comprising four variables which included 50 data points each were used to establish this empirical relation. The model shows a good fit to the numerical modeling data (r2 = 0.99). Further studies are required in order to test its applicability to waste dumps of Goa more generally. An unstable dump slope has the potential to create a number of environmental issues. If the slope is structurally unstable (as discussed in this paper), or its surface is prone to soil erosion, transportation of mine waste to off-site areas may occur; this is a situation operators are keen to avoid. The latter issue is generally addressed by surface stabilisation measures.

123

Environ Earth Sci

The importance of maintaining stable slopes becomes clear when considering the work of Juwarkar et al. (2003), Kumar et al. (2003) and Yellishetty et al. (2009) into the heavy metal and acid-producing mineral content of mine waste found in Goa (Table 1). If this waste, devoid of plant-supporting nutrients and carrying high concentrations of heavy metals, is washed into the local area the sequential social and environmental effect would be devastating.

Conclusion The effect of heavy monsoonal rainfall on waste dump stability has been assessed. It has been shown through numerical modeling that the influence of monsoon rainfalls on the factor of safety of a dump slope is very dramatic (Fig. 5). When free flowing overburden material is dumped, it was observed that a slope angle of 30–35° was formed. An empirical model has been developed to help predict the occurrence of deep-seated waste dump slope failures caused by monsoonal rains and the resulting raised water table. This paper shows that an increase in compaction of the material during the construction of the dump will lead to dramatic increases in the stability of the dump slope. The stability of a waste dump is crucial not only to prevent personal injury or death, asset loss or damage, but also detrimental downstream environmental effects. The possible environmental impacts of a dump collapse have been summarised. With some dumps containing high heavy metal concentrations and acid-producing minerals a failure to contain them within a stable dump can poison downstream water supplies and dramatically effect crop yields. Although further research is required to examine the stability of mine waste dumps in monsoon affected areas, it is hoped that this research and the empirical relation developed will serve as a rapid indicator of potential slope instabilities and demonstrate the effectiveness of increased compaction of waste material during dump construction. Acknowledgments Mohan Yellishetty duly acknowledges the logistic support extended by the management Sesa Goa Limited. Special thanks are due to US Tilve, MK Patil and Leena Vernekar. Finally, the help rendered by staff of CESE and Department of Civil Engineering, IIT Bombay is acknowledged. He would also like to acknowledge the help of Shyam R Asolekar, PG Ranjith and Scott Gould.

References ASTM (2004a) Standard test method for density of soil in place by the drive-cylinder method, ASTM D2937 ASTM (2004b) Standard test methods for particle-size distribution (gradation) of soils using sieve analysis, ASTM D6913-04e2

123

ASTM (2005) Standard test methods for laboratory determination of water (moisture) content of soil and rock by mass, ASTM D2216 ASTM (2006a) Standard practice for classification of soils for engineering purposes (unified soil classification system), ASTM D 2487 ASTM (2006b) Standard test methods for specific gravity of soil solids by water pycnometer, ASTM D854-06 ASTM (2007a) Standard practices for preserving and transporting soil samples, ASTM D4220-95 ASTM (2007b) Standard test method for unconsolidated-undrained triaxial compression test on cohesive soils, ASTM D2850-03a ASTM (2007c) Standard test methods for laboratory compaction characteristics of soil using modified effort, ASTM D1557-07 ASTM (2007d) Standard test methods for particle-size analysis of soils, ASTM D422-63 Caldwell JA, Moss ASE (1981) The simplified analysis of mine waste embankments. Symposium on design of non-impounding mine waste embankments, Denver, USA Caruccio FT, Hossener LR, Geidel G (1998) Pyretic materials: acid drainage, soil acidity, and liming. Reclamation of surface mined lands 1, CRC Press, pp 159–190 Chaulya SK, Chakraborty MK, Ahmad M, Singh KKK, Singh RS, Tewary BK, Gupta PK (1999) Water resource accounting for an iron-ore mining area in India. Environ Geol 39(10):1155–1162 Cho SE, Lee SR (2001) Instability of unsaturated soil slopes due to infiltration. Comput Geotech 28:185–208 Cho SE, Lee SR (2002) Evaluation of surficial stability for homogeneous slopes considering rainfall characteristics. J Geotech Geoenviron Eng 128(9):756–763 Chu J, Bo MW, Chang MF, Choa V (2002) The consolidation and permeability properties of Singapore marine clay. J Geotechn Geoenviron Eng ASCE 128(9):724–732 Davis GB, Ritchie AIM (1987) A model of oxidation in pyritic mine wastes: part 3: import of particle size distribution. Appl. Math. Model 11:417–422 Fourie AB, Rowe D, Blight GE (1999) The effect of infiltration on the stability of the slopes of a dry ash dump. Geotechnique 49(1):1–13 Gavin K, Xue J (2008) A simple method to analyze infiltration into unsaturated soil slopes. Comput Geotech 35:223–230 IBM (1995) Disposal of solid waste in Indian mines. Information circular no. 2, Indian Bureau of Mines, Ministry of Mines, Government of India IBM (2002) Indian Minerals Year Book, Indian Bureau of Mines, Ministry of Mines, Government of India Juwarkar AA, Singh SK, Dubay K, Nimje M (2003) Reclamation of iron mine spoil dumps using integrated biotechnological approach. In: Proceedings of national seminar on status of environmental management in mining industry, I.T.-B.H.U., Varanasi, Jan 17–18, pp 197–212 Krahn J (2004) Stability modeling with SLOPE/W: an engineering methodology. GEO-SLOPE/W International Ltd, Canada Kumar V, Jadhav GN, Dutta D, Manna SS, Rao SM, Shetty SN (2003) Mineralogy applied to the processing and utilization of high alumina, iron-ores. In: International seminar on mineral processing technology (poster), Panjim, Goa, Feb 6–8 Ng CWW, Wang B, Tung YK (2001) Three-dimensional numerical investigations of groundwater responses in an unsaturated slope subjected to various rainfall patterns. Can Geotech J 38:1049–1062 Rahardjo H, Lim TT, Chang MF, Fredlund DG (1994) Shear-strength characteristics of a residual soil. Can Geotech J 32:60–77 Rassam DW, Williams DJ (1997) Geotechnical characterisation of mine waste. In: Bouazza AA, Kodikara J, Parker RJ, Balkema AA (eds) Proceedings of 1st Australia–New Zealand Conference

Environ Earth Sci on Environmental Geotechnics, Melbourne, Australia, Nov 26–28, pp 459–464 Robertson MA (1986) Mine waste disposal: an update on geotechnical and geohydrological aspects of waste management, a geotechnical report by Steffan, Robertson and Kirsten Engineers, Vancouver, pp 1–24 Smith EE, Shumate KS (1970) Sulfide to sulfate reaction mechanism. Fed Water Qual Admin Water Poll Control Res series report #14010 FPS, 02/70 Sobek AA, Schuller WA, Freeman JR, Smith RM (1978) Field and laboratory methods applicable to overburdens and mine soils. US Environmental Protection Agency, EPA-600/2-78-054, p 203 Williams DJ (1996) Role of geomechanics in minesite rehabilitation. In: Jaksa MB, Kaggwa WS, Cameron DA (eds) Proceedings of 7th Australia New Zealand Conference on Geomechanics:

Geomechanics in a changing world, Adelaide, Australia, 1–5 July, Canberra, Institution of Engineers pp 850–856 Wu TH (1995) Slope stabilization. In: Morgan RPC, Rikson RJ (eds) Slope Stabilization and erosion control a Bioengineering Approach. E & FN Spon, London, pp 221–264 Xue J, Gavin K (2008) Effect of rainfall intensity on infiltration into partly saturated slopes. Geotech Geol Eng 26:199–209 Yellishetty M (2004) Iron ore overburden management in Goa mines, Dissertation, Indian Institute of Technology, Bombay Yellishetty M, Karpe V, Reddy EH, Subhash KN, Ranjith PG (2008) Reuse of iron-ore mineral wastes in civil engineering constructions: a case study. Resour Conserv Recycl 52:1283–1289 Yellishetty M, Ranjith PG, Kumar DL (2009) Metal concentrations and metal mobility in unsaturated mine wastes in mining areas of Goa, India. Resour Conserv Recycl 53:379–385

123