Coal Mine Overburden Dump Research Articles

A Critical Review on Static and Dynamic Performance of Coal Mine Overburden Dump Slopes: Present Status and Way Forward

ABSTRACT In the last two decades, opencast coal mining has dominated the coal mining sector of India in comparison to the underground mining. This has caused an increase in large quantity of overburden (OB) waste material which is generally dumped in the form of slope commonly known as OB dump slope. The highly heterogeneous OB dump materials are generally dumped in the loose state implying that the OB dump slopes are highly vulnerable to failure. Therefore, proper functioning of the mining activities requires stable OB dump slopes. This paper briefly provides an overview on the formation of OB dump slopes and some catastrophic failures highlighting the importance of proper and adequate analyses. Next, the major factors affecting the OB dump stability are discussed elaborately with respect to the performance of the slopes under static and dynamic loading. Finally, various approaches available for the assessment of their stability are collated and discussed. The important aspect of consideration of heterogeneity on the performance of slope is highlighted and the need of detailed future research is envisaged.

Bearing Pressure Assessment of Shallow Foundation on Coal Mine Overburden Dump with Spatial Variability Considerations

Bearing Pressure Assessment of Shallow Foundation on Coal Mine Overburden Dump with Spatial Variability Considerations

Effect of grass species root for enhanced slope protection in amended coalmine overburden dump soil

Effect of grass species root for enhanced slope protection in amended coalmine overburden dump soil

Mine soil properties as influenced by tree species and topography of the re-vegetated coal mine overburden dump

Re-vegetation or natural succession of plant species is an important factor of soil development in postmining overburden dumps. As the parent material (sedimentary rocks and regolith) is more or less uniform in the dump, the topographic position and vegetation are the major factors that affects the mine soil quality. Accordingly, this study was designed for a relative evaluation of the influence of dump topographical position (crest, backslope, toeslope) and tree species (Azadirachta indica, Cassia siamea, and Leucaena leucocephala) on soil quality. Trees growing on the toeslope of the dump were significantly taller with larger diameter at breast height than those at backslope or crest. Soil moisture, pH, total S, available P, and Fe content were significantly (P < 0.05) affected by topographical position of the dump. All these properties were higher in the toeslope, except S in the crest. Tree species affected all the soil properties, except electrical conductivity and Mn. Organic carbon content was significantly lower for the nitrogen fixer L. leucocephala (2.03 %) than A. indica (3.30 %) or C. siamea (3.39 %). Soil dehydrogenase activity (39.79 mg TPF/24hr/kg) and microbial biomass carbon (286 µg/g) was higher under L. leucocephala, and C. siamea, respectively. Based on redundancy analysis (RDA), 87.5 % of the data variation is explained by the tree species, whereas, only 12.5 % by the topography. Principal component analysis revealed that C. siamea contributes significantly for the variation in soil properties of the dump. Re-vegetated plant species are a dominant factor of soil development in post mining dump than the topographical position. C siamea and the toeslope are closely associated with soil microbial biomass carbon. It is recommended to plant C. siamea with relatively higher planting density in crest and backslope than toeslope of the dump.

Effect of blast induced vibration on coal mine overburden dump slope through discrete element method

Blast induced ground vibration (BIGV) is a serious threat for the coal mine overburden (OB) dump slopes. The problem becomes intricate considering heterogeneity of the OB dump materials. The performance of an OB dump slope under BIGV is investigated considering Voronoi tessellation scheme of universal distinct element code (UDEC) for the heterogeneity of the OB materials. Variations of BIGV, expressed in terms of peak particle acceleration, velocity and displacement, with the density of explosive and the distance of OB dump slope from the blasting source are comprehensively reported considering single-benched as well as double-benched OB dump slopes. Nonlinear dynamic analyses are carried out considering the expected BIGV at the base of the OB dump slope and effects of blasting parameters on the performance of the dumps were investigated considering different monitoring points along the surface of the slope. The effects of heterogeneity on the dynamic response of OB dump slopes are also presented in comparison with the homogeneous condition. A comparative study based on the performance of single-benched and double-benched slopes under BIGV is also presented. Finally, the failure state of the OB dumps were inferred from the permanent ground displacement experienced by the slopes considering BIGV. The methodology and the presented results are supposed to be beneficial for the mining authority in framing the safety guidelines for OB dump slopes in coal mines.

Investigation of root traits of Dendrocalamus strictus cultivated on organically amended coalmine overburden and its potential use for slope stabilization

The active and abandoned coalmine overburden (OB) dumps are prone to slope instability under the influence of external agents. Estimating the mechanical reinforcement imparted by the grassroots on the coalmine overburden dumps is vital. This paper discusses the effect of organic amendment on the growth characteristics and root distribution of native grass Dendrocalamus strictus species (common name: Bamboo) in the Jharkhand region, India. A pot experiment was conducted wherein the OB was amended with different proportions of cow dung (OA) and garden soil (GS) to be used as growth substrates known as treatments (T1-T5). A pot having only GS (T6) was used as a control. The growth of six D. strictus saplings under each treatment was monitored for survival, shoot height, and canopy area. The root distribution, root area ratio (RAR) with depth, root tensile strength (Tr ) vs. root diameter (d) relationship, and variation of additional cohesion (root cohesion, cr ) with depth were studied for each species (Wu method). The pot experiment shows that the chosen grass can survive on the OB dumps with a suitable external amendment and can exhibit a well-developed root system and produce higher root reinforcement when allowed to grow under unrestricted conditions.

A novel approach for mobile kentledge loading in plate load tests on coal mine-over burden dumps

Acute space crunch in the mining places lead to use of overburden dumps for rehabilitation and construction of new structures. Evaluation of stability and bearing capacity is of prime concern in utilization of these overburden dumps for further construction activities. In this study, the use of novel mobile plate load test for determining the bearing capacity of mine over burden dumps is discussed in detail. Conducting conventional plate load tests with traditional kentledge load is a costly, time-consuming, and necessitate huge workmanship. To overcome these setbacks, in this study the mine-excavator is modified to mobile kentledge loading arrangement. Using this novel approach, the time for testing is reduced by about 90% and the cost of work is reduced by about 200% with safe working environment. Further, the bearing capacity results are compared with the corresponding values obtained through standard Terzaghis estimation methods. Results obtained through Terzaghis method are found to be over conservative compared to the in-situ Plate load test evaluations. Thus, through this study it is recommended to perform enough plate load tests to conclude the actual bearing capacity and settlement of mine over-burden dumps that are non-homogenous and filled in an unscientific manner. Further, the safe ultimate bearing capacities were used for understanding the safety against capacity enhancement for probable rise in height of mine over burden dumps.

In-situ investigation on coal mine overburden dump slope and its seismic stability considering heterogeneity

Stability of the coal mine overburden (OB) dump slopes is many times compromised owing to the lesser availability of the in-situ characteristics of the OB dump materials and their spatial heterogeneity. In this study, multi-channel analysis of surface waves (MASW) investigation was carried out for the characterization of OB dump materials of Jambad opencast coal mine of India and the variation of heterogeneous in-situ characteristics has been reported in terms of statistical parameters. Next, the stability of a two-bench OB dump slope against seismic forces was investigated through finite element limit analyses coupled with random field theory utilizing Karhunen-Loeve expansion method for the spatial heterogeneity of the OB dump material. The effects of spatial heterogeneity of the OB dump material on the probability of failure and the critical pseudostatic seismic coefficient of the slope were investigated through Monte-Carlo simulations. The influence of spatial heterogeneity of OB dump materials were investigated with both isotropic and anisotropic correlation lengths. Finally, seismic slope stability analyses were also carried out using the discrete element method for the size heterogeneity of the OB dump materials. This study summarizes the effects of heterogeneity of material property and size on the seismic stability of OB dump slope.

Correction to: Probabilistic assessment of effects of heterogeneity on the stability of coal mine overburden dump slopes through discrete element framework

Correction to: Probabilistic assessment of effects of heterogeneity on the stability of coal mine overburden dump slopes through discrete element framework

Probabilistic assessment of effects of heterogeneity on the stability of coal mine overburden dump slopes through discrete element framework

Probabilistic assessment of effects of heterogeneity on the stability of coal mine overburden dump slopes through discrete element framework

Reclamation of Coal Mined Land with Integrated Biological Approach

A pilot study was conducted at a backfill area of coal mine overburden dump (OBD) in Tikak Colliery, North Eastern Coal Field, Margherita, Assam, India, to evaluate the performance of 42 native plant species in a revegetation experiment with integrated biological approach during 2018-2021. The plantation was done with application of lime @ 15 gm per pit and farm yard manure (FYM) @ 2 kg per pit and planting nursery raised inoculated seedlings with arbuscular mycorrhizal fungi (AMF) and plant growth promoting rhizobacteria (PGPR) after a series of pot experiments. Pot culture experiments were done to obtain the best treatment combination for the field trails. The seed ball technology was also adopted in the initial year to stabilize the area with green herbaceous cover and to improve soil parameters. The result revealed that herbaceous species growing from seed ball sowing could survive in the OBD area. The best performed treatment combination was AMF + PGPR + Lime + FYM. Out of a total of 42 native plant species 17 were recorded for 60- 70 % survival after 2 years of planting on the OBD site. These practices completely replaced the application of topsoil in the revegetation programme of coal mine site and may be replicated for reclamation of OBD site for successful plantation programme.

Effect of Scattered Dumping of Soft Soil in Coal Mine Overburden Dumps: A Probabilistic Analysis

Effect of Scattered Dumping of Soft Soil in Coal Mine Overburden Dumps: A Probabilistic Analysis

Evaluation of contamination of manganese in groundwater from overburden dumps of Lower Gondwana coal mines

Inappropriate management of coal mine overburden (OB) dumps creates environmental hazards. In many countries, high concentration of Mn was observed in groundwater near the coal mine OB dump sites. Comparatively new coal mines in Barjora coalfield were chosen in this study to assess the impact of OB dumps in groundwater. Acid Digestion (AD), Toxicity Characteristics Leaching Procedure (TCLP) and Batch Leaching Test (BLT) were performed to estimate Mn concentration in OB dumps and its leaching behaviour. Shale present in OB dump has potential to leach high concentration of Mn. The aquifer in this region is mainly unconfined type and water table is very shallow. In situ soil is characterized by 44.3% sand, 37.5% silt and 18.2% clay with a saturated hydraulic conductivity of 5.58 cm/day. Column study and HYDRUS 1D numerical modelling were used to simulate the migration of Mn in vadose zone. Subsurface soil does not possess appreciable attenuating potential to retard the transport of Mn in vadose zone. HYDRUS 1D model explains that 1.6 m thick soil profile of the study area may release Mn in groundwater after 11th year and it can attain the complete breakthrough at 17th year. A groundwater contaminant transport model based on available hydrogeological data has been developed using VISUAL MODFLOW 2009.1 software. The movement of Mn in aquifer has been determined using MT3DMS code. It indicates ≃ 8 km2 area around the two Open Cast Coal Mines (OCCMs) namely OCCM 1 and OCCM 2 may suffer groundwater contamination of Mn by 2050.

Phytostabilization of coal mine overburden waste, exploiting the phytoremedial efficacy of lemongrass under varying level of cow dung manure

A pot study was performed to assess the phytoremedial potential of Cymbopogon citratus (D.C.) Staf. for reclamation of coal mine overburden dump wastes, emphasizing the outcome of amendment practices using cow dung manure (CM) and garden soil mixtures on the revegetation of over-burden wastes (OB). Wastes amendment with cow dung manure and garden soil resulted in a significant increase in soil health and nutrient status along with an increment in the phytoavailability of Zn and Cu which are usually considered as micronutrients, essential for plant growth. A significant increment in the total biomass of lemongrass by 38.6% under CM20 (OB: CM 80:20) was observed along with improved growth parameters under amended treatments as compared to OB (100% waste). Furthermore, the proportionate increases in the assimilative rate, water use efficiency, and chlorophyll fluorescence have been observed with the manure application rates. Lemongrass emerged out to be an efficient metal-tolerant herb species owing to its high metal-tolerance index (>100%). Additionally, lemongrass efficiently phytostablized Pb and Ni in the roots. Based on the strong plant performances, the present study highly encourages the cultivation of lemongrass in coal mining dumpsites for phytostabilization coupled with cow-dung manure application (20% w/w).

Use of biopolymers to enhance the geotechnical properties of coal mine overburden waste

Many conventional methods of soil/waste treatment are available that have a negative impact on the ecosystem. Natural polymers (biopolymers) are considered as eco-friendly and sustainable grouting additives that strongly react with water to produce a viscous suspension. This research study investigates the influence of biopolymer on the undrained shear strength and hydraulic characteristics of coal mine overburden dump, which is widely considered for the construction of embankments and water-retention structures around mines. Two biopolymers were employed, xanthan and guar gum, over a range of concentrations (0·25–1·5%). Experimental results indicate the significant enhancement of shear strength parameters with an increase in concentration and the curing period. Permeability tests, carried out for a long term, also showed a change in hydraulic conductivity values, which are dependent on biopolymer concentration and the ageing period. Thus, it can be concluded that the application of biopolymers as temporary seepage barriers for the protection of many geotechnical works (such as foundations) and underground structures is highly beneficial.

Effect of fly ash on geotechnical properties and stability of coal mine overburden dump: an overview

The management of overburden (OB) materials needs proper attention to safe mining operations. Several mine OB dump failures have been occurred due to inappropriate geotechnical and geometrical parameters. Increasing consumption of coal in thermal power plant also generates huge amount of ash which adversely affect the environment and its utilization is a great challenge. The present paper reviews the effect of fly ash on the different geotechnical properties and stability of coal mine OB dump material to explore a safe and effective utilization of fly ash. It was found that up to 30% fly ash can potentially modify the compaction characteristics, California bearing ratio value, unconfined compressive strength, and shear strength parameters of OB dump material. Based on the review, it may be suggested that fly ash-OB mix can be effectively utilized in the mine OB dump and for the mine haul road construction thus, provides an alternative mode of fly ash utilization in huge quantity.

Chronological Variation of Metals in Reclaimed Coal Mine Soil and Tissues of Eucalyptus Hybrid Tree After 25 Years of Reclamation, Jharia Coal Field (India).

Fast-growing metal-accumulating woody trees are potential candidates for phytoremediation of coal mine overburden (OB) dumps. The present study assessed chronological variation in metals (Pb, Zn, Mn, Cu, and Co) concentration in reclaimed mine soil (RMS) and tissues (leaf, stem bark, stem wood, root bark and root wood) of Eucalyptus hybrid tree between 3 and 25-year old OB dumps (RMS3 and RMS25) from Jharia coal field (India). Total metal concentrations of Pb, Zn, and Cu in RMS25 were 1.55, 3.46, and 1.44 times lower (p < 0.05), respectively, than RMS3. Higher concentrations of total (110%-565%) and available form (DTPA-extractable) of metals (109%-480%) were observed in RMS25 than in control soil. Pb selectively accumulated in stem bark, Zn and Mn in leaves, and Cu and Co in root wood. Metal concentrations were higher (1.04-4.15 times at p < 0.05) in tree tissues growing on RMS25 than in RMS3. This study concluded that Eucalyptus hybrid could be utilized for reclamation of coal mine OB dumps.

Differential distribution of metals in tree tissues growing on reclaimed coal mine overburden dumps, Jharia coal field (India).

Opencast bituminous coal mining invariably generates huge amount of metal-polluted waste rocks (stored as overburden (OB) dumps) and reclaimed by planting fast growing hardy tree species which accumulate metals in their tissues. In the present study, reclaimed OB dumps located in Jharia coal field (Jharkhand, India) were selected to assess the accumulation of selected metals (Pb, Zn, Mn, Cu and Co) in tissues (leaf, stem bark, stem wood, root bark and root wood) of two commonly planted tree species (Acacia auriculiformis A.Cunn. ex Benth. and Melia azedarach L.). In reclaimed mine soil (RMS), the concentrations of pseudo-total and available metals (DTPA-extractable) were found 182-498 and 196-1877% higher, respectively, than control soil (CS). The positive Spearman's correlation coefficients between pseudo-total concentration of Pb and Cu (r = 0.717; p < 0.05), Pb and Co (r = 0.650; p < 0.05), Zn and Mn (0.359), Cu and Co (r = 0.896; p < 0.01) suggested similar sources for Pb-Cu-Co and Mn-Zn. Among the five tree tissues considered, Pb selectively accumulated in root bark, stem bark and leaves; Zn and Mn in leaves; and Cu in root wood and stem wood. These results suggested metal accumulation to be "tissue-specific". The biological indices (BCF, TFleaf, TFstem bark and TFstem wood) indicated variation in metal uptake potential of different tree tissues. The study indicated that A. auriculiformis could be employed for Mn phytoextraction (BCF, TFleaf, TFstem bark and TFstem wood > 1). The applicability of both the trees in Cu phytostabilization (BCF > 1; TFleaf, TFstem bark and TFstem wood < 1) was suggested. The study enhanced knowledge about the selection of tree species for the phytoremediation of coal mine OB dumps and specific tree tissues for monitoring metal pollution.

Eco-restoration of coal mine overburden dump

Energy is needed for economic growth and more than 70% of the energy generation capacity in India is by using coal. The production of coal was 430.83 Mt out of which opencast contributed to around 373 Mt in 2006 with an estimated overburden removal of 600 million m3. In India, opencast mining is most prominent method of coal excavation. However, each year hundreds of acres of pristine forest and productive agricultural land are brought in the gambit of open cast coal mining. Moreover, open cast mining leaves behind a lot of over burden which is an environmental problem. Faced with a burgeoning population, agriculture in India must bring under its gambit the non-conventional or non-traditional area, to feed the teeming millions. Reclaimed coal mine areas could be the non-traditional areas. Among the two methods of restoration, physical methods are costly and not viable. Biological methods are of low cost hence most appropriate. Among biological technique using tree species to restore coal mine spoil holds great promise because it accelerate the soil-forming processes, control erosion, build up organic matter, develop microbial communities, initiate nutrient cycling, decreases air and water pollution, reduces geo-environmental disasters, maintain biodiversity and enhance overall aesthetics of the area.

Plant species from coal mine overburden dumping site in Satui, South Kalimantan, Indonesia

Coal mine overburden (OB) materials were nutrient-poor, loosely adhered particles of shale, stones, boulders, and cobbles, also contained elevated concentration of trace metals. This condition cause OB substrate did not support plants growth. However, there were certain species that able to grow on overburden dumping site. This investigation sought to identify plants species that presence on coal mine overburden. The research was conducted on opencast coal mine OB dumping site in Satui, South Kalimantan. Vegetation sampling was carried out on six different ages of coal mine OB dumps (7, 10, 11, 42, 59 and 64 month) using line transect. Species identification used information from local people, AMDAL report of PT Arutmin Indonesia-Satui mine project, and website. There were 123 plant species, consisted of 79 herbs (Cyperaceae, Poaceae and Asteraceae), 10 lianes, bryophyte, 9 ferns, 10 shrubs, and 14 trees. A number of Poaceae, i.e., Paspalumconjugatum , Paspalumdilatatum , and Echinochloacolona generally present among the stones, boulders, and cobbles. While Cyperaceae such as Fimbristylis miliaceae , Cyperus javanicus , Rhyncospora corymbosa and Scleria sumatrensis most often foundinand around thebasin/pond with its smooth and humid substrate characteristics. Certain species of shrubs and trees present on the 7 month OB dumping site. They were Chromolaena odorata , Clibadium surinamense , Melastoma malabathricum , Trema micrantha , and Solanum torvum (Shrubs), Ochroma pyramidale and Homalanthus populifolius (trees). This plant species could be used for accelerating primary succession purpose on coal mine overburden dumping site. Nevertheless, species selection was needed to avoid planting invasive species.