Indian Coal Mines Research Articles

Lessons learnt from Indian inundation disasters: An analysis of case studies

Mining industry, has been a topic of increasing attention in the last few decades. The disasters of the past years due to different causes push for a moment of reflexivity about learning from accidents. The increased interest in improving the safety at workplace has been driven mainly by a series of recent mining disasters that have occurred in India as well as in the rest of the world. Disasters in Indian coal mines have caused havoc in the past. In recent times also, there had been 7 disasters since the year 2000 killing 144 persons. The worst disaster ever in Indian mining history is the Chasnala disaster due to inundation in 1975, killing 375 persons. But unfortunately we have learnt very little from these past disasters. The authors in this paper had tried to identify the thrust area along with the gaps in our learning system, which need more attention for maintaining safety by analyzing the past three disasters due to inrush of water in Indian coal mines including Chasnala coal mine disaster, greatest disaster of India mining industry and tried to highlight the weaknesses in the system and key lessons learnt from them.

Establishment of blasting design parameters influencing mean fragment size using state-of-art statistical tools and techniques

Abstract In the present study, principal component analysis (PCA) and stepwise selection and elimination (SSE) techniques were used to establish significant parameters (blasting design, rock and explosive) in surface coal mines by reducing dimensionality and variables from a host of blasting parameters. Mean fragment size (MFS) prediction models were subsequently developed using multiple linear regression (MLR) analysis technique. The two constructed and proposed models adequately selected relevant blast design, explosive and rock mass parameters. The performances of these models were assessed through the determination coefficient (R 2 ), F-ratio, standard error of estimate and root mean square error (RMSE). The PCA technique has shown good promise in eliminating the redundant parameters and in selecting relevant blast design parameters. Hierarchical cluster analysis technique was used for confirming the similarity of blasting design parameters in two trial blasting data set. The results were tested and validated with the 19 actual blast data set at acceptable correlation levels and have been illustrated in the form of figures, tables and graphs. MFS prediction equations based on PCA and SSE techniques were simple and suitable for practical use in overburden bench blasting of Indian coal mines.

Studies on failure behaviour of wire rope used in underground coal mines

Wire ropes operate at high stress levels and are almost invariably subject to fluctuating loads. The continuous degradation of wire rope affected with operative services will ultimately lead to failure. Study of the causes of failure of two wire ropes from two different Indian coal mines have been carried out and discussed here. The investigating parameters comprises of physical examination, wear & corrosion, lubrication, macro & micro-examination and chemical composition. The investigation revealed that the major cause of failure was due to excessive wear and corrosion resulted in high reduction in diameter ranging from 50%–90% and poor lubrication condition of wire rope. Micro-examination also revealed intergranular corrosion with cracks and pittings, uniform corrosion with pitting along the grain. Further elongated grain which was indicative of stress due to excessive corrosion with sudden impact resulted in its failure.

Open-pit coal mine production sequencing incorporating grade blending and stockpiling options: An application from an Indian mine

ABSTRACTProduction scheduling is a crucial aspect of the mining industry. An optimal and efficient production schedule can increase the profits manifold and reduce the amount of waste to be handled. Production scheduling for coal mines is necessary to maintain consistency in the quality and quantity parameters of coal supplied to power plants. Irregularity in the quality parameters of the coal can lead to heavy losses in coal-fired power plants. Moreover, the stockpiling of coal poses environmental and fire problems owing to low incubation periods. This article proposes a production scheduling formulation for open-pit coal mines including stockpiling and blending opportunities, which play a major role in maintaining the quality and quantity of supplied coal. The proposed formulation was applied to a large open-pit coal mine in India. This contribution provides an efficient production scheduling formulation for coal mines after utilizing the stockpile coal within the incubation periods with the maximization of discounted cash flows. At the same time, consistency is maintained in the quality and quantity of coal to power plants through blending and stockpiling options to ensure smooth functioning.

Analysis of occupational health hazards and associated risks in fuzzy environment: a case research in an Indian underground coal mine

This paper presents a unique hierarchical structure on various occupational health hazards including physical, chemical, biological, ergonomic and psychosocial hazards, and associated adverse consequences in relation to an underground coal mine. The study proposes a systematic health hazard risk assessment methodology for estimating extent of hazard risk using three important measuring parameters: consequence of exposure, period of exposure and probability of exposure. An improved decision making method using fuzzy set theory has been attempted herein for converting linguistic data into numeric risk ratings. The concept of ‘centre of area’ method for generalized triangular fuzzy numbers has been explored to quantify the ‘degree of hazard risk’ in terms of crisp ratings. Finally, a logical framework for categorizing health hazards into different risk levels has been constructed on the basis of distinguished ranges of evaluated risk ratings (crisp). Subsequently, an action requirement plan has been suggested, which could provide guideline to the managers for successfully managing health hazard risks in the context of underground coal mining exercise.

Performance evaluation of chairlift ropes in two man-riding systems in an incline coal mine using a non-destructive testing instrument

Electromagnetic non-destructive testing/evaluation is an important means for assessment of the performance of chairlift ropes in a mining installation. The visual method produces the possibility of inadequate inspection due to its subjectivity. Magnetic flaw detectors, which measure loss of metallic area (LMA) and detect local faults (LF), such as broken wires and other faults of the ropes, are used to determine rope wear. Regular non-destructive evaluation/testing (NDE/NDT) inspections provide a powerful tool for monitoring the rate of degradation of a rope. The effective technology for these devices depends on the magnetic properties of the steel wire rope. An attempt has been made in this paper to evaluate the performance of ropes in two chairlift man-riding systems in an incline coal mine in India.

Dispersion of methane in tailgate of a retreating longwall mine: a computational fluid dynamics study

Methane layering is a critical issue for underground coal mines. It can lead to methane explosion and trigger massive explosion of coal dust. This paper presents the computational fluid dynamics (CFD) simulation study on dispersion of methane layer in tailgate of a retreating longwall mine panel considering the methane emission rate from an underground coal mine in India. Distribution of methane-air mixture velocity and dispersion of methane in the tailgate were investigated at air velocities varying in the range of 0.5–3.0 m/s at 0.5 m/s intervals. The study revealed that ventilation plays a significant role on methane dispersion in underground coal mines and a minimum air velocity of 3.0 m/s is required for lowering the average methane concentration in the tailgate to a safer level. The adequacy of ventilation for preventing methane layering was examined in terms of methane layering number. The simulation results were compared with the experimental data obtained from a full-scale coal mine and fairly good agreement between them was observed. It is envisaged that this study can greatly improve the understanding of methane layering and methane dispersion phenomena in underground coal mines.

Soil carbon development in rejuvenated Indian coal mine spoil

The impact of mine spoil on the landscape is significant, as excavated rock-debris is commonly disposed in heaps that blanket the original land surface. Spoil heaps destroy the original soil habitat releasing soil-bound carbon, which is difficult to re-estate when mining operations cease and restoration begins. The present work follows the development of vegetative cover on a coalmine spoil tip in India over a period of 19 years following restoration. The potential of re-vegetated the mine spoil to imbibe carbon is examined through the development of above- and below-ground biomass development. It was observed that the soil organic carbon and microbial biomass carbon (MBC) significantly increased with re-vegetation age, with above ground biomass increasing by 23 times, and belowground biomass increased by 26 times during the period of study. Soil organic carbon and MBC increased by 4× and 6.6× times, respectively. The average calculated annual carbon budget was 8.40T/ha/year, of which 2.14T/ha was allocated to above ground biomass, 0.31T/ha to belowground biomass, 2.88T/ha to litter mass and 1.35T/ha was sequestered into the soil. This work has shown that the development of biomass following the restoration of mine spoil was significant and that considerable quantities of carbon were stored in above and below ground plant matter, and in the soil itself. It is concluded that appropriate restoration strategies can be used to rapidly establish a viable, healthy and sustainable ecosystem that imbibes carbon into former mine-impacted land.

Investigation of Cycle Time Segments of Dragline Operation in Surface Coal Mine: A Statistical Approach

Dragline is highly capital intensive equipment to procure, operate and maintain in any surface mining operation. Given this, every second of operation of this capital intensive equipment is absolutely important. Improvement of even a single second in the total cycle time has a tremendous bearing on the overall performance of this equipment. In this light, the present paper is an endeavour to critically analyze the cycle time of dragline operations in a major surface coal mine in India. Rigorous statistical analysis has been performed on individual cycle time segments, of complete dragline cycle. The segmental cycle times have been found to be statistically significant and appear to be best represented by lognormal, normal and beta distributions. Furthermore, the mean time of the statistical distribution for segmental cycle time of dragline has revealed the dependence of cycle time on cut geometry and depth. Results have been illustrated in the form of figures, graphs and tables.

Rationalising postural demand of side discharge loading machine operators with respect to musculoskeletal pain and discomfort in underground coal mines in India

Cardiac and postural strain of 12 healthy side discharge loader (SDL) operators is evaluated at varied depth of working during their actual work. A comparative statement is made on working heart rates (WHR), relative cardiac cost (RCC), net cardiac cost (NCC) and recovery heart rates (RHR) of miners. Mean WHR is within 132-138 bpm with a corresponding mean RCC between 43 and 46% for the one group of miners and about 34-37% for another group of miners. The job seemed to be 'heavy' to 'extremely heavy' in accordance with job heaviness scales. Existing heat stress in terms of effective temperature (ET) is above the recommended limits proposed by WHO in case of Mine A and ET value is within the recommended limits in Mine B. SDL operators in coal mines are exposed to excessive physical strain and heat stress. Therefore, ergonomic interventions are required to minimise such strain.

A comparative study of removal of fluoride from contaminated water using shale collected from different coal mines in India

Low-cost water defluoridation technique is one of the most important issues throughout the world. In the present study, shale, a coal mine waste, is employed as novel and low-cost adsorbent to abate fluoride from simulated solution. Shale samples were collected from Mahabir colliery (MBS) and Sonepur Bazari colliery (SBS) of Raniganj coalfield in West Bengal, India, and used to remove fluoride. To increase the adsorption efficiency, shale samples were heat activated at a higher temperature and samples obtained at 550°C are denoted as heat-activated Mahabir colliery shale (HAMBS550) and heat-activated Sonepur Bazari colliery shale (HASBS550), respectively. To prove the fluoride adsorption onto different shale samples and ascertain its mechanism, natural shale samples, heat-activated shale samples, and their fluoride-loaded forms were characterized using scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffraction study, and Fourier transform infrared spectroscopy. The effect of different parameters such as pH, adsorbent dose, size of particles, and initial concentration of fluoride was investigated during fluoride removal in a batch contactor. Lower pH shows better adsorption in batch study, but it is acidic in nature and not suitable for direct consumption. However, increase of pH of the solution from 3.2 to 6.8 and 7.2 during fluoride removal process with HAMBS550 and HASBS550, respectively, confirms the applicability of the treated water for domestic purposes. HAMBS550 and HASBS550 show maximum removal of 88.3 and 88.5%, respectively, at initial fluoride concentration of 10mg/L, pH3, and adsorbent dose of 70g/L.

Assessment and Modelling of Dust Concentration in an Opencast Coal mine in India.

<div> <p>Dust pollution is a major problem in opencast mines. Many activities are associated with generation of dust that makes a cloud of pollutant at the work environment and the surrounding areas. Activities as drilling, blasting, transportation, surface miner etc. are the principle sources of generation of dust in mines. This paper focuses on the monitoring of dust level at different operational areas of the mine, characterization of dust collected from different sources, personal exposure of dust and finally prediction of dust concentration at different locations of the mine and nearby areas using AERMOD software. The study was conducted at Lakhanpur opencast mine of MCL (Mahanadi Coalfields Limited), a subsidiary body of CIL (Coal India Limited) the largest coal producing company of the world. The study was done in the month of December 2013, using DustTrakII at nine different locations in the mine. The quartz content of dust was determined using FTIR analysis. Personal Dust Sampler (PDS) was used to determine the personal dust exposure value for different workers. Dust dispersion modelling was done by using AERMOD and isopleths were plotted.</p> </div> <p> </p>

Resistivity imaging technique to investigate the subsurface strata conditions due to blasting in underground coal mines in India

ABSTRACTProduction from underground coal mining in India has been decreasing since the last three decades. Blasting‐off‐the‐solid, in Indian underground mines, has been a widely practised method for winning coal while developing mine galleries in bord and pillar system. The blast holes are drilled in solid coal without free face in blasting‐off‐the‐solid method of mining and are blasted with permitted types of explosives and delay detonators. Blasting‐off‐the‐solid will play an important role in underground coal production. The mines that were planned earlier to be away from residential areas are now approaching to those areas. The coal reserves are being exploited very fast, and mine owners cannot ignore to take the coal beneath the structures/houses. In this paper, resistivity imaging technique has been used to document the change of subsurface structures/features between the surface and underground face, where blasting is carried out to extract the coal in underground coal mines. Resistivity imaging survey conducted at three mining sites revealed that there was no significant change in subsurface strata conducted during pre‐ and post‐blasting conditions. The slight change in resistivity values up to 35 Ωm up to a few metres of peripheral area of the blasting face in the mine may be either due to the effect of blast vibration and/or same void created by blasting or increase in porosity of overlying subsurface strata.

A CRITICAL STUDY ON AVAILABILITY AND CAPACITY UTILIZATION OF SIDE DISCHARGE LOADERS FOR PERFORMANCE ASSESSMENT

Improvement in production and productivity has become an important aspect for today’s coal industry especially in case of underground coal mines. The record of production and productivity of Indian underground coal mines over the years is dismal, to say the least. Mechanization in loading system has made possible major breakthroughs in underground coal mining technology. Side Discharge Loaders (SDL) is now used as a loading machine for intermediate mechanization in underground coal mining. To meet the production and productivity issues the SDL machine should be maintained effectively and efficiently to have maximum availability. Higher availability of machine shall enable optimum utilization thus increasing production and productivity of these capital intensive items.. This paper intends to identify and highlight the various factors and problems affecting performance of SDL machine. Further an attempt is made to calculate the percentage availability and utilization of SDL deployed in underground coal mines and analyzes the contributing factors to improve the overall efficiency. In addition, the problems of SDL application, breakdown and its management have also been identified and resolved in these studies to propose suitable measures for improving them.

Qualitative Assessment of Strata Control in an Indian Underground Coal Mine

A prerequisite to reduction in the number of roof/side fall occurrences—a stated goal of DGMS for enhancing workmen safety in underground coal mines—is risk identification through application of appropriate assessment techniques. This article presents the outcome of a study undertaken to identify, analyse and evaluate the roof/side fall risks. WRAC and Risk Matrix tools have been used to provide a qualitative measure of the risk magnitude. Outcomes of a case study performed in an Indian underground coal mine are presented in the present work. It could be inferred that hazard severity increased because of the existence of “geological disturbances and weak roof and sides”. Operational lacunae, such as non-determination of RMR, non-framing of SSR, and non-availability of support material, enhance roof/side fall risks.

Seepage Modeling for a Large Open Pit Coal Mine in India

Medapalli Open Cast Project (MOCP) owned by M/s Singareni Collieries Company Limited (SCCL), Andhra Pradesh, India where “Highwall mining” is practiced lies in the immediate vicinity of a large perennial river, ‘Godavari’. The mine and river, which are only 140–150 m apart, an artificially constructed embankment, built above highest flood level, restricts the water leakages into the mine. A need to know seepages that may occur at active working faces of MOCP highwall mining faces, referred here as web holes/web cuts, is realized and this seepage modeling study is undertaken. Since the coal mine has “Barakar formations” which, in general, has watery field conditions, there exists an enhanced possibility of seepage or water inflow into the mine pit. For this reason also this predictive assessment study of seepage modeling became essential. The quantitative estimation of water is done by conceptualized model of mine which was based on the sub-surface geology and hydrological set up of the area. SEEP/W module of ‘Geostudio’ software is used for prediction, estimation and assessment of water flux, inflow and recharges quantities as it is capable to consider the saturated/unsaturated flow conditions for the encountered unconfined aquifers. In the modeling exercise, we used ‘steady state’ and ‘transient state’ conditions to determine the water quantities of the seepage faces at pit walls/web holes. The estimation so done for this coal mine is compared and verified by another popular “Ground water flow and contaminant transport and river modeling software” namely, MODFLOW. Briefly and concisely, this study concludes that the water seepage from river to mine pit is very less and hence it has no adverse effect on the web holes and web pillars of highwall mining faces. The results of this study had helped mine management in taking decision about (a) uninterrupted operation of ‘highwall miner’ at the coal extraction faces, (b) safe extraction of the locked in coal between river and mine, (c) developing and designing safe work places for both man and machinery, (d) achieving targeted coal production as per production schedule, (e) effective drainage and utilization of mine water as per the action plan of mine. Thus, on account of seepage water any harm/damage to already deployed, ‘highwall miner’ is very remote and the coal wining operation at MOCP is safe. The mine planning can be done easily using estimated water quantities and mine faces can be kept dry during maximum period in a year.

Assessment of pot-hole subsidence risk for Indian coal mines

Ground subsidence induced by extraction of coal seam belowground brings about changes in surface environment leading to trough and pot-hole subsidence. Pot-hole subsidence is extremely hazardous and does not give any prior indication before its occurrence. In India, several pot-holes have occurred in the coal mines of South Eastern Coalfields Limited triggering the need for in-depth studies. In line with the requirement, literature review and field investigations were conducted to develop an in-depth understanding of various parameters influencing the occurrence of pot-holes. The critical parameters identified were rock to soil ratio, depth to height of extraction ratio, brittleness index of rock and rock density. Risk assessment of pot-hole subsidence has been done by developing an empirical rating approach named as pot-hole subsidence rating (PHSR), involving the critical parameters with suitable corrections for certain structural and mining conditions to obtain corrected PHSR (CPHSR). CPHSR was then applied for all the 34 pot-holes studied and it was found that all the pot-holes fall under Class I and Class II category of risk representing a very high to high risk class. An effort was made for the estimation of pot-hole depth utilizing the developed CPHSR in both the development and depillaring cases. The developed approach was found to yield consistent results in pot-hole depth prediction.

Chip Size Characterization for Selecting Optimum Production Parameters of Surface Miner Operating in a Coal Mine

Coal production using surface miner technology is a well-accepted method today in Indian coal mines contributing a sizeable proportion to the overall production. Production of coal chips of desired size is an important parameter in surface miner performance evaluation in terms of tonnes per hour as well as fulfilment of the need of the consumers. The demand for an average chip size in the range 100-150 mm thermal power plants is growing and this size also fetches a premium price compared to blasted lumpy coal. A field study was conducted at Sonepur Bazari opencast mine, Eastern coalfields (ECL), West Bengal, India for evaluating the cutting operation and performance of a 2200 SM surface miner under varied operational and rock mass conditions. An imaging technique coupled with Fragalyst software was used for grabbing and analysing the sizes of chips produced by surface miner. The wide variation in chip size formation observed in the field was due to the fluctuations in cutting speed and also the presence of joints. This communications reports the study carried out on surface miner to develop a new methodology for characterizing chip size, fixing the optimum machine operating parameters for a desired chip size and also the production potential.

MineVue radar for delineation of coal barrier thickness in underground coal mines: Case studies

Disaster due to inundation is one of the major threats of coalmines. Sudden heavy inrush of high volume of water from the unapproachable and unknown waterlogged workings in underground mines is defined as inundation. There have been several instances of inrush of water due to old galleries getting connected by new development headings, resulting in disasters involving heavy fatalities and loss of machines. This type of disaster has occurred in many coal producing countries and may occur in future until a suitable tool to investigate barriers thickness is in regular use. Directorate General of Mines Safety (DGMS) has stipulated that a safety barrier thickness of not less than 60 m must be maintained between abandoned workings and contemporary mine developments. It has been estimated that a large number of underground coal mines in India are under threat of adjacent unknown waterlogged mine workings. Therefore, evaluation of barrier thickness up to 60 m is essential to prevent mine disasters due to inundations. Considering the above facts, a new GPR system named MineVue radar is developed having depth of penetration of 60 m subject to geo-mining conditions of Indian coalmines first time in the world. Final trial of the developed MineVue radar system was done at the Kachhi Balihari Colliery in Bharat Cocking Coal Limited (BCCL), Dhanbad. The validation of GPR data in the known mine sites were done with accurate existing mine-plans to establish the reliability and confidence of mine operators, policy makers and safety personnel.

Study and Analysis of Accidents Due to Wheeled Trackless Transportation Machinery in Indian Coal Mines – Identification of Gap in Current Investigation System

Mining is one of the most hazardous industries amongst where the rate of casualty is still very high from work place accidents. A large number of mobile mining equipment such as haul trucks, dumpers, tractors, tankers are used for different operation and such operations contribute significantly in causation of fatal and serious accidents. In this study, 33 years ‘fatal accident data from Indian coal mines were analyzed from 1980. The rate of fatal accident shows a significant reduction from 1980 to 2000 but it becomes almost flat for the last 13 years since 2000. Though all the accidents were investigated and recommendation were made for preventing recurrence, there is no further reduction in the rate in last 13 years which reflects the gaps in our investigation procedure or recommendation or implementation. An effort has been made in this paper to highlight the major gaps in the existing investigating procedure and thereby making useful recommendations to ensure effective control measures in place to reduce the risk to an acceptable level.