Geoenvironmental and Geotechnical Issues of Coal Mine Overburden and Mine Tailings

Inhaltsverzeichnis

1. Frontmatter

2. Chapter 1. Geotechnical Considerations of Mine Tailings Management through Mine Backfilling

   Seneth Jayakodi, Nagaratnam Sivakugan, Peter To

   Abstract

   Mine tailings generated during mining should be handled effectively as a simultaneous process with the mining operation. Mine tailings management with a minimum impact to the environment is a vital aspect of sustainable mining, and this can be mainly done by constructing tailing dams and/or backfilling of underground stopes. However, the later provides more unique and supportive advantages to the mining operation over the former, and hence, mine backfilling has been a popular and successful method worldwide in managing mine tailings over the decades. The choice of materials utilised for backfill operation depends on the location of backfilling, availability of materials for a particular fill and prevailing ground conditions. Hydraulic fills and Paste fills are the two most common types of mine fills used in backfill systems. During backfilling stresses are developed within the fill in the mine stope and they are influenced by soil arching. Prior to backfilling, the horizontal drives of the mine are barricaded with competent retaining walls to prevent backfill material entering other areas of the mine. An overview of mine backfilling, backfilling strategies, types of mine fills and their properties with more focus on hydraulic fills, typical backfill system and its behaviour, stress developments within backfills, loadings on drive barricades and barricade construction, drainage considerations of backfills, challenges in mine backfilling and future prospects are discussed in this chapter.

3. Chapter 2. CPTu-Based Soil Behaviour Type Indexes that are Independent of Sleeve Friction Readings: An Application in Tailings

   Luis Alberto Torres-Cruz, Nico Vermeulen, Abideen Owolabi

   Abstract

   The piezocone penetration test (CPTu) is widely used for in situ geotechnical characterisation. One of the most common uses of the CPTu is the characterisation of the soil stratigraphy. Assessment of the stratigraphy is often aided by two-dimensional charts that are divided into regions that correspond to different soil behaviour types. The implementation of these charts can be facilitated by soil behaviour type (SBT) indexes which are functions of the parameters that plot along the two axes of the SBT charts. These functions are defined in such a way that contours of the function coincide, at least approximately, with the internal boundaries of the SBT charts. It appears that the two best known SBT indexes are a function of the sleeve friction reading of the CPTu. Herein we raise awareness around two additional SBT indexes that are independent of sleeve friction. These additional SBT indexes may be useful supplements to the better-known indexes that depend on sleeve friction measurements. The implementation of the indexes is illustrated using CPTu data from iron ore tailings although the concepts discussed herein are applicable to any type of soil.

4. Chapter 3. Assessment of Mine Overburden Dump Stability Using Numerical Modelling

   Tarun Kumar Rajak, Laxmikant Yadu

   Abstract

   This work aims to analyze the appropriate dump geometry for successful mining operations and proper management of OBD material in external dumps, taking into consideration stability issues. In order to achieve this the strength properties of the OBD material were investigated through a laboratory investigation when mixed with various quantities of fly ash and Ground Granulated Blast Furnace Slag (GGBS). The FLAC/Slope software was utilized to assess the stability of external dumps containing different amounts of OBD material, fly ash, and GGBS. To determine the Factor of Safety (FOS), the dump geometry, which had an overall height of 120.0 m, was numerically simulated at various bench and slope angles. To forecast the FOS accurately, various models, including the Multiple Linear Regression Model (MLR) and the Artificial Neural Network (ANN) model, were developed. The mix proportions comprising 68% OBD material, 20% fly ash, and 12% GGBS demonstrated the highest cohesiveness value. The angle of internal friction decreased significantly with increasing concentrations of fly ash and GGBS. Through numerical modeling, it was found that for the OBD material with 10% fly ash, maximum dump capacity could be achieved with two benches at heights of 60.0 m and bench slopes of 32°. The developed MLR model and ANN model (N9) with an architecture of 6-14-14-1 predicted the FOS with excellent accuracy, with coefficient of determination values of 0.9863 and 0.9968, respectively.

5. Chapter 4. Performance of Coal Mine Overburden Dump Slope Under Earthquakes Using Extended Finite Element Method Based Voronoi Tessellation Scheme

   Madhumita Mohanty, Rajib Sarkar, Sarat Kumar Das

   Abstract

   The occurrence of earthquakes in coal mining areas endangers the stability of the overburden (OB) dumps. This leads to the damage of mining properties, disturbance in mining activities and loss of lives. Ultimately, the production time of the desired amount of coal gets delayed. Owing to the heterogeneous nature of the OB dump, the proper determination of its material properties becomes difficult. In the present work, the opencast coal mine in Jambad, India has been considered to be the study area. Thus, the properties of materials based on multi-channel analysis of surface waves (MASW) investigation have been used in the numerical analyses. The size and shape heterogeneity of the OB dump particles was represented by means of the extended finite element method (XFEM) based Voronoi tessellation scheme using the two-dimensional geotechnical software RS2. In order to consider a wide range of strong ground motion parameters, a set of ten earthquakes were selected for performing the dynamic analyses of a double-benched OB dump. The influence of peak ground acceleration (PGA) on the amplification ratio at various key points of the OB dump was estimated and compared taking into account the heterogeneous and homogeneous OB dumps. The guidelines prepared for the coal mine OB dumps are entirely silent on the effect of earthquakes, therefore this study would be useful in framing of the guidelines considering the influence of earthquakes on the coal mine OB dump slopes.

6. Chapter 5. Slope Stability Analysis of Coalmine Overburden Dump Using a Probabilistic Approach

   Ashutosh Kumar, Sarat Kumar Das, Lohitkumar Nainegali, Krishna R. Reddy

   Abstract

   During process of coal mining, overburden materials are removed to reach the coal seam. Overburden materials are composed of soil, rock, and other debris that are stored in the vicinity of the mining area in the form of dumps. These materials are often heterogeneous, hence their properties such as density and strength can vary greatly from one location to another. Thus, to assess the stability of the overburden dumps, a probabilistic analysis is desired over a deterministic analysis. In this study, a typical overburden dump geometry has been considered where the top 1 m of the slope is considered to comprise vegetation. A 2D limit equilibrium analysis has been performed where the material heterogeneity has been incorporated by considering the probabilistic descriptors i.e., mean, standard deviation, and coefficient of variation (CoV). The effect of CoV on the overburden and vegetative layer material properties is studied at different intervals using Monte Carlo (MC) method. The results obtained are compared with the results of the bare dump slope (without vegetation). The factor of safety from the deterministic analysis and the probability of failures for various cases for the bare and vegetated dump slope are compared. The findings offer significant perspectives on comprehending how the slope stability assessment of coal mine dumps is affected by material heterogeneity and a vegetative layer.

7. Chapter 6. Suitability of Bauxite Residue as a Landfill Liner Material—An Overview

   Narala Gangadhara Reddy, Tayyaba Siddiqua, Manikanta Devarangadi, Chandra Bogireddy

   Abstract

   Bauxite residue (also known as red mud) is a by-product obtained during the production of alumina. The landfill liners are widely known as hydraulic barriers which attenuate the flow of leachate/contaminant migration into the groundwater. It is imperative to study the geotechnical engineering properties of the landfill liner and needs to be examined. This chapter reviews the use and application of bauxite residue as a landfill liner material. The geotechnical and environmental engineering properties of bauxite residue have been studied from the literature and its suitability has been assessed based on the criterion limits suggested by the United States Environmental Protection Agency (USEPA). The engineering properties such as particle size distribution, compaction properties, hydraulic conductivity, strength, adsorption characteristics and leaching characteristics have been presented. Further, the suitability of bauxite residue to be used as a landfill liner with different additives and research needs also have been discussed. This review study suggests that bauxite residue could be a potential landfill liner material as it satisfies the criterion limits. However, the use of any bauxite residue should be evaluated individually on a case-by-case basis.

8. Chapter 7. Fly Ash Based Geopolymer Modified Bitumen (GMB) binder—An Overview

   Bojjam Sravanthi, N. Prabhanjan

   Abstract

   The basic materials (bitumen binder) used in pavement construction will have great strength, thanks to a new technology called geopolymerization. Instead of using natural resources, industrial byproducts were used to create the geopolymer. According to the literature, an alkaline activator was used to activate a geopolymer bituminous binder that contained fly ash (FA). To achieve good strength and resistance to deformation, bitumen is modified with geopolymers. Based on a number of research studies, bituminous binder was used in place of 0, 3, 5, and 7% of the geopolymer in order to investigate the physical characteristics and performance of fly ash-based GMB by performing various tests on its ductility, penetration, viscosity, and dynamic shear rheometer. From the literature, it may be inferred that virgin binder is weaker than GMB that has had a 5% modification. In addition to increasing bitumen binder strength and reducing deformation, the geopolymer mix also has an impact on sustainability, economic advantages, maintenance costs, and environmental advantages.

9. Chapter 8. Mineral Carbonation of Mine Tailings for Long-Term Carbon Capture and Storage

   Faradiella Mohd Kusin, Verma Loretta M. Molahid

   Abstract

   This chapter emphasizes on mineral carbonation technology applicable to the mining industry. The content discusses the utilization of mine tailings as the feedstock for carbon sequestration through the mineral carbonation process. The concept is in line with carbon capture and storage (CCS) technology, which can be integrated into mine processing and reclamation. CCS by means of mineral carbonation is an effective method for sequestering atmospheric carbon dioxide for long term and has been regarded as a beneficial approach in combating climate change. This chapter outlines the potential feedstock materials for mineral carbonation, use of mine tailings in carbon sequestration and the factors that can influence the mineral carbonation process. The process of mineral carbonation using different types of feedstocks ranging from Ca/Mg/Fe-based minerals and waste materials in different operating conditions are discussed. Examples from the use of mine tailings such as limestone waste, iron ore and gold mine waste as feedstock for mineral carbonation are also presented. It has been clear that mine tailings may serve as reservoir or sinks for long-term carbon storage in mitigating the impact of carbon dioxide emission. This approach would be useful for a low-carbon future in the mining sector which is essential in meeting the long-term target for environmental sustainability.

10. Chapter 9. Environmental Sustainability Assessment of Alternative Controlled Low Strength Materials as a Fill Material

    Anshumali Mishra, Sarat Kumar Das, Krishna R. Reddy

    Abstract

    Controlled low strength material (CLSM) can be used as a backfill material while constructing utility trenches. Numerous research suggested integrating industrial waste products in the design of these cementitious mixtures for CLSM. This study compares various CLSM designs that incorporate industrial byproducts to a traditional aggregate backfill design and perform a comparative sustainability assessment of them. In the present study environmental sustainability assessment of alternative CLSM materials has been assessed for a proposed utility trench of depth 3 m, width 3 m, and stretch of 100 m in Dhanbad Municipal Corporation. The assessment has been carried out using Ecoinvent 3.0 database, TRACI 2.1 as the midpoint impact method through a commercially available environmental sustainability assessment tool SimaPro 9.4.0.2. The study incorporated the streamline approach of cradle to gate. It was observed that the impact of coal mine overburden based controlled low strength material (CLSM_OB) is the most sustainable option for the backfill material with relative 39% impact in ozone depletion, 41% fossil fuel depletion, and 65% ecotoxicity. In addition, the relative impact on human health is 80%, ecosystem quality is 52%, and resource depletion is 67% by CLSM_OB, followed by CLSM_FS, CLSM_WTS, and M5 Concrete in increasing order of impact.

11. Chapter 10. State of the Art Review on the Geochemical, Microbial and Environmental Aspects of Passive Acid Mine Drainage Treatment Techniques

    M. K. Kaushik

    Abstract

    Acid Mine Drainage (AMD) mainly occurs as a result of the natural oxidation of Iron-sulfide minerals contained at operating or closed/decommissioned mine sites, which is one of the most significant environmental challenges faced by the mining industry people worldwide. AMD adversely affects the surrounding land use and water quality due to its typical low pH, elevated concentration of metals, reactive sulfide content, and high acidity.

    This study presents a state-of-the-art review of the Geochemical, Microbial, and Environmental aspects of AMD generation, collection, and cost-effective options for its treatment (source control to minimize acid generation, implementation of mitigation control, and treatment). This paper also provides an overview of Constructed wetlands (CWs) and phyto remediation options that could provide efficient passive low-cast viable treatment options with a higher percentage of sulfide reduction, removal of other metals, and alleviation of extreme acidic conditions for the developing, operating as well as closed/decommissioned mines.

    Thus, indigenous aquatic macrophytes and microbial communities that immobilize, bio-leach, or accumulate a small number of metals in constructed wetlands treatment could effectively contribute to the remediation of acidic metal-contaminated runoff waters from mines and mine waste processing/disposal areas. Thus, indigenous aquatic macrophytes and microbial communities based on an integrated constructed wetlands bioremediation approach may successfully lead to a cleaner, greener environment.

12. Chapter 11. Acid Mine Drainage and Metal Leaching Potential at Makum Coalfield, Northeastern India

    Sk. Md. Equeenuddin, S. Tripathy, Prafulla Kumar Sahoo, M. K. Panigrahi

    Abstract

    Acid mine drainage (AMD) is one of the primary environmental concerns in the coal mining industries. It is relatively more common in the coalfield deposited influenced by marine environment. The Makum coalfield, the largest Tertiary coalfields in India, is located in Assam and well known for generating AMD. The assessment of potential AMD has been done using the acid base accounting (ABA) study which serves as the principal tool for predicting the post mining water quality. In this paper a detailed mineralogical study of overburden, the static ABA test for both coal and overburden samples along with their leaching studies have been conducted. The coal seams and laminated carbonaceous shale contain significant amount of pyrite. Mineralogical study of the overburden reveals that dolomite is the dominant controlling mineral with trace amounts of calcite for neutralizing the acid generated by the oxidation of pyrite. The relatively higher amount of dolomite is found to be associated with siltstone and non-laminated (massive) carbonaceous shale. The ABA results indicated that all the coal seams, and few overburden materials have acid generating potential. Concentration of Cr, Cu, Mn, Ni, Pb and Zn in overburden is above their respective crustal abundances. However, Pb is above its crustal abundance in coal. Leaching experiment infers that overburden containing high pyrite has more potential for releasing metals relative to those having less pyrite. Concentrations of Mn, Ni and Pb in the leachate are found to be much higher than their respective water quality guideline. Abnormally high concentration of Mn is found to be associated with the dissolution of siderite. Coal releases significantly high concentration of Ni. The results of ABA and leachate study are nearly consistent with the direct mine discharge quality.