Indian Mines Research Articles

Assessment of the Strength of Inclined Coal Pillars through Numerical Modelling based on the Ubiquitous Joint Model

The inclined coal pillars, formed during the underground extraction of the inclined coal seam, are different from the flat coal pillars due to the high strength anisotropy of the inclined bedded rock, and the asymmetrical stress distribution. To ease the manoeuvring of the men and machinery in the inclined coal mine, the pillars are developed along the apparent dip. Thus, the pillars become rhombus-shaped with acute-angled corners which crush rapidly due to the high stress concentration. No suitable formula is found to estimate the strength of the inclined coal pillar that incorporates all these factors. Thus, the use of the available coal pillar strength formulae may endanger the extraction of the inclined coal seams. This study elucidates the procedures to estimate the strength of the inclined coal pillars by the numerical modelling technique. The ubiquitous joint model is used to simulate the shearing characteristics of the inclined strata. The parametric study shows that the strength of the inclined coal pillars decreases with the increase of the dip of the coal seams. It is also obtained that the strength of the pillars decreases with the decrease of the value of the acute angle of the corners. The peak stress distribution and the strain accumulation over the inclined pillars at the time of failure are plotted in three-dimensional graphs which show the asymmetrical characteristics of the inclined coal pillars. The analysis of variance shows that the dip of the coal seams and the acute angles of the corners have a statistically significant effect on the strength of the inclined coal pillars. Based on the results of the simulation, the best fit relation is established by the multivariate non-linear regression technique to estimate the strength of the inclined coal pillars. The coefficient of determination (R2) and the root mean square error of the model are obtained as 0.92 and 0.065, respectively. The validation of the developed model has been carried out by the stable and failed inclined pillar cases of different underground inclined coal mines in India. Comparisons of the safety factors, obtained from the developed model and the flat pillar strength formula, indicate that the flat pillar strength formula overestimates the strength of the inclined coal pillars. The developed model can be used to design the inclined coal pillars for safe extraction of inclined coal seams.

Manufacturing Consent: Mining, Bureaucratic Sabotage and the Forest Rights Act in India

ABSTRACTThis article traces how substantive decision-making power over extractive projects is denied to India’s indigenous and forest-dwelling communities, even as they have clinched rights to ownership and consent under the landmark Forest Rights Act of 2006. By examining the consent mechanism provided under the act, we contend that the possibilities, and limits of such mechanisms are shaped by the larger architecture of the state-bureaucratic apparatus and practices that govern the process of transferring forests (“forest diversion” in bureaucratese) from rural communities to corporations. By analyzing a case of a forest diversion proposal for an iron ore mine in India’s resource-rich state of Odisha, we argue that consent provisions are derailed by “bureaucratic sabotage,” i.e. the power of corporations and state officials to control and manipulate the movement and circulation of documents through different tiers of government. In conclusion, we offer some thoughts on the weaknesses of the FPIC mechanism and the possible ways to address some of these. However, ultimately, the larger implication of such sabotage is the headlong collision between FPIC provisions and the principle of eminent domain. For FPIC to be meaningful, in India and globally, this fundamental contradiction must be confronted and resolved in favor of resource justice.

Fractal and seismic b-value study during dynamic roof displacements (roof fall and surface blasting) for enhancing safety in the longwall coal mines

Mining of coal has always been a very risky task from older times and, is often associated with various fatal accidents in form of rock bursts, gas outbursts, slope/bench failure. Studies carried out by various safety agencies around the world such as MSHA (USA), DGMS (India), State Administration (China), have reported higher fatality rates in underground mines, and are mostly resulting from the sudden roof falls. Most of the roof falls occur suddenly in the running mine due to support failure or adverse strata conditions. The present study focuses on the monitoring of the roof falls in the longwall mine of Central India, as the presence of stable roof has resulted in several roof fall related accidents in various Indian longwall panels including Churcha mine, Kothadi mine and GDK-11A incline. The aforesaid accidents was also responsible for the poor performance of longwall mines in India, which is considered to be one of the best mining practices in majority of the coal producing countries of the world. The paper incorporates the spatial distribution and magnitude of microseismic events released before/during the roof falls and surface blasting in terms of Fractal Dimension as well as b-value. These two parameters helped in getting precursory signatures for spatio-temporal forecasting of minor and major roof falls, as well as helped in monitoring strata behavior during surface blasting. A total of sixty-four minor falls (LF1-LF64), seventy-six major falls (RF1-RF76) and fifteen surface blasting (SB1-SB15). The results showed decreasing trend in the both Fractal Dimension (D) and b-value before roof fall, as microseismic events emitted were highly clustered and had higher magnitude. Whereas, higher Fractal Dimension (D) and lower b-value was seen during surface blasting, when the emitted microseismic events had higher magnitude but were found to be dispersive in nature.

Better accounting of greenhouse gas emissions from Indian coal mining activities — A field perspective

Fugitive methane emissions from coal mining activities have been frequently talked about in the literature due to concerns about climate change. However, indirect and direct CO2 emissions may also result from coal mining processes. The indirect CO2 emissions include those from diesel combustion from equipment while direct CO2 emissions are a relatively new area of research and have been recently brought into the purview of the Intergovernmental Panel on Climate Change (IPCC) inventory guidelines. We discuss some of the preliminary results which can give some directions into the potential research areas for better accounting of greenhouse gas emissions from coal mining activities. These have been derived from practical studies undertaken at selected coal mines in India.

Beneficiation of Manganese Ore Using Froth Flotation Technique

Abstract The present study is contemplated to develop a method for flotation of low grade Manganese Ore. Both manual and mechanized workings of manganese mines in India by open cast and underground mining & dump working methods. Froth flotation is the process generally recommended for the beneficiation of low and medium grade ores because of the floatability characteristics of the manganese. The present work has been taken with waste Manganese ore from Garividi mines (Vizianagaram District). Manganese ores of major commercial importance are pyrolusite (MnO2, Mn about 63.2%) & psilomelane. From this study the recovery of MnO2 by using froth flotation technique was (85.41%) achieved. The optimum time of flotation obtained for manganese is 9 minutes. At 9 minutes, the optimum variables obtained are collector dosage of 2.5 gm/ml of feed and frother 2 gm/ml, depressant 1.5 gm/ml and pH is 8. The frother dosage has shown marginal effect on flotation of manganese ore. The collector dosage has shown significant effect on flotation of manganese ore. Flotation of manganese ore shows fine particle size of 45 µm give recovery of 85.41% at optimum variables. Natural pH of manganese ore in the flotation process gives better recovery than the higher pH.

Spatio Temporal Variation of Air Pollutants in the North East Coalfield areas under Indian Coal Mines

This is a part of the project which developed an Information & Communication Technology based software application tool focused and addressing the issues related with the preparation of Environmental Monitoring Report and Environmental Management Plan in North-Eastern Coalfields under Coal India Limited. It addressed mine water treatment with cost analysis, Overburden Dump Management along with the parameters of Air, Water, Effluent Water, and Soil. This user friendly software tool enabled with GIS or Geographical Information System.The present paper dealt with the air pollution and its variations in a spatio-temporal scenario. In a highly vegetation domain which covered not only by forests but also wild life and tea gardens, air pollution played a pivotal role in maintaining the ecological balance, specially for micro organisms. Therefore the work opened a broad scope of research from air pollution to micro organism balance in an eco sensitive region.

Evolution of digital detonators as an intelligent tool for control blasting in Indian mines

Evolution of digital detonators as an intelligent tool for control blasting in Indian mines

Occupational Exposure of Noise Level in Opencast Iron Ore Mines in India

Mining in general has become essential industry sector for the sustaining growth of any developing country. In India iron ore mining is mainly mechanised and well developed industry sector, using highly mechanised equipments and technology for excavation and processing of mined iron ore. It is due to this reason iron ore mining seen as a one of the major sector responsible for workplace occupational health hazard particularly for noise related health impacts on workers health. The objective of this study was to ascertain the job specific noise exposure among the Similar Exposure Groups (SEGs). Total 133 personal noise dosimeter samples were collected from different job category and working areas of iron ore mining and processing sector. It was observed that the participated workers in the crushing area were exposed to 81.64 dB (A), Heavy Earth Moving Machineries (HEMM) operators 86.10 dB (A), loading plant workers 83.76 dB (A), screening plant workers 87.62 dB (A) and mines operation and workshop workers 84.92 dB (A). During the study specifically HEMM operators were highly exposed to workplace noise, with 46% samples exceeding warning limit and 18% exceeding danger limit prescribed by Directorate General of Mines Safety (DGMS), Government of India. It was felt necessary to augment the awareness and safety training to the workers for proper implementation of preventive measure for workplace noise exposure.

The vibration health risk assessment on operators of different capacity dumpers at opencast mine in India

In a labour intensive sector, some of the factors in the work environment which impact the health of vehicle operators include: Whole-Body Vibration (WBV) and Hand-Arm Vibration (HAV). The vibrations transferred from the dumpers are harmful to the operators; hence a study was carried out to measure the vibration from dumpers and its effect on operators in Indian opencast mines. Dumper is a vehicle designed to transport bulk material and used extensively in the construction and mining industries. For the measurement, dumpers with the different capacities were selected from the opencast mines. Vibration measurements were carried out in accordance with ISO 5349-1 for the measurement of HAV and ISO 2631-1 for the measurement of WBV. The obtained WBV exposure result shows that the problem of musculoskeletal disorder was significantly higher with respect to VDV(8) (69 %) in the exposed population as compared to A(8) r.m.s. acceleration (46 %). Moreover different capacity dumper vehicle hand transmitted vibration through steering wheel, A(8) r.m.s. acceleration observed in the range of 1.91 m/s2-4.28 m/s2. As per EU DIRECTIVE 2002/44/EC, specified Exposure Action Value (EAV) 71 % measured A(8) value falls within EAV limit. However, despite of the result operator experience problem of hand arm vibration syndrome. Hence there is a need of ergonometric deign enhancement on dumpers vehicle’s seat and steering wheel.

Evaluation of the Effect of Fault on the Stability of Underground Workings of Coal Mine through DEM and Statistical Analysis

The rock mass around an excavation is generally traversed by different geological discontinuities such as faults, folds, slips, joints, etc. Fault is one of the major geological discontinuities which creates lot of difficulties during underground winning of coal. Entire stress regime and ground conditions in the formation are altered in and around the faults. Faults also impose detrimental effects by introducing impurities, including clay and various forms of mineral matter into the coal seams; opening of pathways for the influx of water and gas into the underground workings; displacing the coal seams upward/downwards making the coal seams difficult or sometimes impractical to mine. Appropriate evaluation of the effect of the fault on the stability of the underground workings is a requisite for safe design of the underground mining structures. In this paper, a study has been carried out to assess the effect of the fault on the stability of underground coal mines by numerical simulation with distinct element method (DEM). On the calibrated DEM model, parametric study has been performed by varying the selected parameters, the dip and the friction angles of the fault. The analysis of variance (ANOVA) shows that both the factors have statistically significant effect on the strength of the coal pillar. Similarly, the displacement of the immediate roof and the height of the disturbed strata are evaluated by the DEM modelling and statistical analysis when the fault passes through the middle of the gallery. The results of ANOVA for both cases indicate that the both factors have significant effect on the displacement of the immediate roof and the height of the disturbed strata. It is obtained from the study that the low angle fault causes high instability in the immediate roof. The paper has been supplemented with the field observations where instability in underground roadways of a coal mine in India is caused by the fault. It was observed in VK-7 incline mine of Singareni Collieries Company Limited, India that there was sudden failure of immediate roof of a roadway where a low angle fault crosses the middle of the roadway. The findings of the paper help to understand the behaviour of the coal pillar and the surrounding rock mass in the presence of the fault. The study would also help to take appropriate decisions about the unstable regions of the working safeguarding safety in underground coal mines.

Coal mine gas: a new fuel utilization technique for India

ABSTRACTMethane is associated with the coal has caused disaster in underground coal mines all over the world. However, coal mine gas utilization for fuel is a well-proven technology. Due to the different compositions of mine gas (0.1–95% CH4), this technology is still in a developing stage in India. Based on mine-specific measurement of the rate of emission, all the underground coal mines in India have been categorized into Degree I, Degree II, and Degree III. Coal mine methane is a general description for all methane released prior to, during, and after mining operations. As such, there is considerable variability in flow rate and composition of the various gas emissions during mining operations. From extraction technology and utilization perspective, coal mine gas is classified into four categories: (1) virgin coalbed methane or pre-mining degasification, (2) coal mine methane or degasification of working seams, (3) ventilation air methane, (4) abandoned mine methane. It is useful to explore the entire range of uses for all forms of coal mine gas to maximize the viability of each opportunity. Coal mine gas utilization/mitigation technologies are divided into five board categories: natural gas substitution, direct use at or near the mine site, electricity generation and cogeneration, chemical feedstock and simple destruction. Opportunities of implementation of these options in India have been discussed in this paper. This study will help to motivate both applied and theoretical research work on coal mine gas sites in India and after detailed analysis, it will provide basic data to interested industries.

A Laboratory Study on Estimation of Shear Strength and Compaction Properties of Overburden Dump Material in Indian Coal Mines

The study investigates the effect of various soil mixtures, mostly found in the overburden material of coal mines, on the strength parameters and compaction properties. Samples were prepared in laboratory to represent both the soil-type and the rock-type waste dump material by mixing shale, sandstone and clay in varying proportions at an interval of 10% each. Samples from two coal mines located at different geographical locations in the eastern part of India were collected and the shear strength (cohesion and friction angle) and compaction parameters (Maximum dry density, MDD and Optimum moisture content, OMC) of the specimens were determined from laboratory study at moisture content around their OMC and analysed. The results so establish that the shear strength parameters for mixtures containing shale are less sensitive to changes and follows rather a flat curve when plotted against their respective material content in the mixture when compared to that containing clay. However, the compaction parameters were found to follow different trends when plotted against the constituent material (shale, sandstone and clay) content of the mixture.

Spatial statistics, spatial correlation and spatial graph theory in air pollution

Abstract The aim of the study is to estimate the particle concentration variation across different working levels inside an opencast mine. The study was conducted in one of the deep opencast copper mines in India to estimate the distribution of different size of particles emitted from the operations concentrated in deeper parts of the mine. Moreover, with advancement of SPSS (version 25), the analytical techniques were used to identify the exposure to different size of particle during mining operations. We introduced the spatial statistic and graph theory in the field of air pollution to understand the particle distribution. The combination of correlation and one-way ANOVA statistical methods were used to estimate the impact of depth of mine as a critical factor on distribution of particle concentration. The outcomes of the study shows that spatial statistics, correlation, one-way ANOVA and graph theory can be used to understand the distribution pattern (shortest route to travel), to estimate concentration at different level, and to better understand mine workers exposure to particle matter.

Estimation of Rock Load in Development Workings of Underground Coal Mines – A Modified RMR Approach

Underground coal mining in India contributes to a share of 55 Mt production with more than 500 mines in operation. In spite of using the well-established CMRI-ISM Rock Mass Rating (RMR dyn ) classification system for roof support design successfully in Indian geo-mining conditions, accidents due to roof fall constitute the major challenge. These failures are generally due to the presence of weak beddings and laminations. Seismic refraction technique (for shallow depth) can be useful in detecting the rock mass conditions. Based on the study a modified rock mass classification system (RMR dyn ) was setup by incorporating field P-wave velocity with a view to arrive at a real ground condition of the in situ rock. Rock loads were also determined in the field to develop a relation with RMR dyn . A comparison of rock load estimation by CMRI-ISM RMR, numerical simulation and RMR dyn clearly depicts that the latter approach is more reliable as the results are close to the actual scenario.

Internationalized Framing in Social Movements against Mining in India and the Philippines

There are several documented cases of indigenous peoples’ conflicts with mining companies, often for the reason that the land planned for mining is sacred or culturally significant to them. This article presents a comparative analysis of two specific anti-mining social movements in India and the Philippines that combined an emphasis on environmental protection with an emphasis on indigenous cultural rights. We show how the emphasis on indigeneity in these social movements played itself out in relation to globalized frames, as well as the other frames within which the movements were also situated.

Application of ANFIS for machinery noise prediction in a bauxite mine

The aim of this study is to predict the sound pressure level (SPL) values from ISO 9613-2, arti?cial neural network (ANN) and adaptive neuro fuzzy inference system (ANFIS) model. For this reason, sound pressure levels produced from the machinery operations were measured in a highly mechanized opencast bauxite mine in India. After collecting the ordered pairs of sound power level, distance, temperature, relative humidity and wind speed, SPL values were determined using ISO 9613-2 method. An endeavour has been made to examine the applicability of the developed soft computing models to predict SPL. To accomplish this objective, data obtained from the machinery operation measurements were assessed by constructing an ANFIS based prediction model. Sound power level (SWL), distance, temperature, relative humidity and wind speed were chosen as the input parameters and SPL as the output of the developed model. SPL prediction capability of the constructed ANFIS model has proved to be effective in terms of performance indices such as root mean square error (RMSE) between anticipated and measured SPL values. Prediction performance comparison has been made between the measured, ISO 9613-2 model, ANN and ANFIS model. The results indicated that the proposed ANFIS model exhibited better prediction performance when compared with ANN prediction model.

Quantifying the benefits of coal mine methane recovery and use projects: Case study on the application of in-mine horizontal pre-drainage boreholes at gassy coal mines in India and the optimization of drainage system design using reservoir simulation

Abstract This article aims to illustrate, through the presentation of case studies, the application of coal mine methane (CMM) drainage technology at two gassy coal mines in India, and to quantify the associated economic and environmental benefits. This work, which is based on two studies developed by the U.S. Environmental Protection Agency (USEPA) through the Global Methane Initiative (GMI), demonstrates that the use of in-mine horizontal boreholes for pre-drainage, capture, and utilization of CMM is both technically and economically feasible. Furthermore, the results show reservoir simulation is a useful tool for optimizing in-mine horizontal pre-drainage borehole placement. The future development and implementation of CMM drainage at each mine has the potential to lower or offset electricity costs, reduce greenhouse gas emissions, unlock coal reserves, and improve mine safety and energy security.

Empirical and probabilistic analysis of blast-induced ground vibrations

An attempt has been made to include an additional blast design parameter, burden, in obtaining the vector peak particle velocity, VPPV. A large set of about 640 blast data pertaining to different rock types from ten different sites in India and Turkey has been collected from the literature. Analysis of these data has been carried out resulting in the proposal of an empirical model for peak particle velocity with due consideration to the burden along with monitoring distance and maximum charge per delay. The performance of the proposed model has been compared with existing models, and the proposed model has been found to serve the purpose of predicting VPPV with greater accuracy. Further, probabilistic analysis of VPPV has been conducted by performing Monte-Carlo (MC) simulation on proposed empirical model. Typical results corresponding to Chittorgarh limestone mines in India are presented. The input parameters namely monitoring distance and maximum charge per delay have been assumed as lognormally distributed random variables, while the burden has been assumed as discreet variable. The analysis of results of MC simulations revealed that output or the state variable, VPPV follows a lognormal distribution. It was possible to take into account the variability in the blast parameters and therefore to study its influence on VPPV.

Spatial and temporal variation of respirable particles around a surface coal mine in India

People living around surface mines are exposed to enhanced respirable particle level. Not many studies are available that evaluated the contribution of mining to it. The paper presented the result of study that investigated spatio-temporal variability of particle concentrations around a surface coal mine in eastern part of India. Particle concentration and concurrent meteorological parameters at 24 locations were measured along four sections from the mine boundary up to 500 m using an aerosol spectrometer and portable weather station. SPSS 20.0 was used for statistical analysis. Average PM10, PM2.5 and PM1 concentration varied in the range 212.67 ± 168.76–524.46 ± 137.57 μg m−3, and 89.53 ± 77.62–297.41 ± 107.10 μg m−3 and 66.22 ± 58.05–246.66 ± 84.26 μg m−3 respectively. This is equivalent to 2.74, 1.34 and 2.77 times the background concentration of PM2.5-10, PM1-2.5 and PM1 respectively. Respirable particles up to 500 m from the mine comprised of 27–73%, 8–12% and 18–61% of PM2.5-10, PM1-2.5 and PM1. During peak production period, the concentration of respirable particles around the mine increased by a factor 5–15 of the average concentrations. Distance and meteorological parameters explained up to 55% of the variability of particle concentration. Present Indian norm to allow an ambient PM10 concentration of 250 μg m−3 at a distance of 500 m is not met, in spite of the study mine is only 10 years old. Extremely limited literature suggests that more studies are required for better understanding and evaluation of mining contribution to the local PM level.

Application of underground microseismic monitoring for ground failure and secure longwall coal mining operation: A case study in an Indian mine

Longwall mining technique has been widely used around the globe due to its safe mining process. However, mining operations are suspended when various problems arise like collapse of roof falls, cracks and fractures propagation in the roof and complexity in roof strata behaviors. To overcome these colossal problems, an underground real time microseismic monitoring technique has been implemented in the working panel-P2 in the Rajendra longwall underground coal mine at South Eastern Coalfields Limited (SECL), India. The target coal seams appears at the panel P-2 within a depth of 70 m to 76 m. In this process, 10 to 15 uniaxial geophones were placed inside a borehole at depth range of 40 m to 60 m located over the working panel-P2 with high rock quality designation value for better seismic signal. Various microseismic events were recorded with magnitude ranging from −5 to 2 in the Richter scale. The time-series processing was carried out to get various seismic parameters like activity rate, potential energy, viscosity rate, seismic moment, energy index, apparent volume and potential energy with respect to time. The used of these parameters helped tracing the events, understanding crack and fractures propagation and locating both high and low stress distribution zones prior to roof fall occurrence. In most of the cases, the events were divided into three stage processes: initial or preliminary, middle or building, and final or falling. The results of this study reveal that underground microseismic monitoring provides sufficient prior information of underground weighting events. The information gathered during the study was conveyed to the mining personnel in advance prior to roof fall event. This permits to take appropriate action for safer mining operations and risk reduction during longwall operation.