Indian Mines Research Articles

Benchmarking energy consumption for dump trucks in mines

Dump trucks are used for transportation in opencast mines and consume about 32% of the total energy use in mines. This paper presents a generic model to benchmark energy consumption for dump trucks in mines. The modelling framework estimates minimum specific fuel consumption (SFC) of dump trucks using mine equipment, engine characteristics and vehicle dynamics. The model investigates the variation of SFC with operating input parameters like payload, material handling rate, vehicle speed, distance, mine gradient, etc. The applicability of the proposed model is illustrated through a case study of multiple dump trucks in a down gradient opencast limestone mine in India. The minimum SFC of 89g/t is estimated for a mine transport system with three excavators and two crushers. The case study shows a potential fuel saving of 17%. The modelling framework developed can be used to set rational targets for energy consumption for dump trucks in mines.

Predictive models for pot-hole depth in underground coal mining—some Indian experiences

Ground subsidence induced by extraction of coal seam belowground brings about changes in territorial environment. This occurs in two forms, namely, trough and pot-hole subsidence. Pot-hole subsidence is extremely hazardous as it does not give any prior indication before its occurrence. Several pot-holes have occurred in the recent past in the coal mines of South Eastern Coalfields Limited and called for a specific study to develop an in-depth understanding of various parameters influencing the pot-hole occurrence for formulating the basis of different predictive models. These critical parameters have been compiled and analysed for seven mines located in different areas of SECL, a subsidiary of Coal India Limited. Multiple regression and artificial neural network (ANN) techniques were used for the preparation of the predictive models to calculate pot-hole depth under different conditions. Different conditions considered in the study are development and depillaring, presence and absence of faults and water bodies. This paper presents the results of the studies carried out in Indian mines representing different geo-mining conditions along with the pot-hole depth prediction models developed. The developed models were validated for a few new cases with the model results matching (within 10 % error in the case of ANN model) with the actual pot-hole depth measured. More varied data sets can fine tune the developed models further.

Need for Clean Coal Mining in India

Mining activity also create tremendous pressure on local flora and fauna particularly where diversion of forest land takes place for mining purposes. The effect of mining on ground water level, silting of surrounding water bodies and land are also great concern. Coal mining contributes largely towards economic development of the nation although it has a great impact upon the human health. It also has its impact on socio-cultural aspect of the workers and people residing in and around coal mining areas. Thus a holistic approach for taking up to mining activities, keeping in mind concerns for adjoining habitats and ecosystem, is the need of the hour. This requires identification of various sites where minerals exist and various factors ranging from appropriate angle of slope of overburden dumps, safe disposal drains, and safe techniques to various silt control structures etc. In India Coal companies are now working towards “clean coal” strategies, which aim to reduce environmental impacts. The reduced ash contents of the washed coal increase the thermal efficiency of combustion. Which in turn make a direct impact on reducing emission of pollutants. However the coal washing requires extra water and it can turn towards a pollution free society.

Processing of Alumina-Rich Iron Ore Slimes: Is the Selective Dispersion–Flocculation–Flotation the Solution We Are Looking for the Challenging Problem Facing the Indian Iron and Steel Industry?

Beneficiation of alumina rich iron ore slimes is a major challenge for the Indian iron ore industry. Considering the limits of gravity and magnetic separation processes in the relatively finer size range in terms of achieving adequate separation efficiency, selective flotation (with and without selective flocculation) of iron ore slimes, which is being used commercially in several countries for the beneficiation of iron ores, is worth exploring for the beneficiation of Indian iron ores. Based on the extensive work carried out in our laboratories, we have concluded that the design and development of highly selective reagents to achieve satisfactory separation of hematite and goethite from alumina containing minerals (gibbsite or kaolinite) in the ore and ore slimes, is the key to solving the challenging problem of processing alumina rich iron ores. Accordingly our research work has been focused on finding/designing selective reagents for iron oxide–gibbsite–kaolinite separation based on a molecular modeling computational approach developed by us for the design of mineral processing reagents. We present in this paper the results of our density functional theory computations to evaluate the interaction energies of a wide variety of different reagent functional groups such as carboxylic acid, hydroxamic acid, phosphonic acid, iminobismethyl phosphoric acid, xanthate and starch with hematite, gibbsite and kaolinite surfaces. Among all the reagents investigated so far, starch exhibits the highest selectivity towards the hematite surface with a difference in interaction energy of ~63 kcal/mol between hematite and gibbsite surfaces. Based on our earlier work which indicated polyvinyl pyrrolidone (PVP) to be more selective dispersant for kaolinite compared to conventional sodium silicate and sodium hexametaphosphate, we have investigated selective flocculation–dispersion of natural iron ore slimes (three different samples obtained from three different mines in India) with PVP and starch reagent combination. The results are promising. While the work is still in progress, the implications of our recent results are discussed in the context of the challenging problem of processing of alumina rich iron ore slimes in India.

Performance evaluation of an independent wire rope core in a cage winder of a mechanized coal mine using nondestructive testing instrument

Nondestructive testing is an important means for assessment of performance of winder ropes. The visual method produces a possibility for inadequate inspection due to its subjectivity. Wire ropes wear out eventually, gradually losing work capability throughout its useful life making periodic inspections, lubrication and tensioning necessary. Magnetic flaw detectors are used to determine rope wearing. They measure loss of metallic area and detect the local faults like broken wires and other faults of the ropes. An attempt has been made in this paper to evaluate the performance of one cage winder rope in a mechanized coal mine in India using nondestructive testing instrument.

Optimization of culture conditions for phosphate solubilization by a thermo-tolerant phosphate-solubilizing bacterium Brevibacillus sp. BISR-HY65 isolated from phosphate mines

Abstract In the present study we isolated and characterized thermo-tolerant phosphate solubilizing bacteria (PSB) having high ferric phosphate (Fe-P) and aluminum phosphate (Al-P) solubilizing abilities for the first time from rock phosphate mines of Jhamarkotra. Optimization for phosphate (P) solubilization by the isolate BISR-HY65 was performed. Different insoluble P sources viz. hydroxyapatite (H-Ap), Al-P and Fe-P along with rock phosphate (RP) from two different mines of India were used to characterize phosphate solubilizing (PSE) abilities. Optimum conditions found were: temperature 50 °C, pH 7.5, xylose as carbon source, ammonium oxalate as nitrogen source and potassium sulfate as potassium source. Phosphate solubilization was found to be associated with the release of organic acids in culture. HPLC analysis of the culture broth at 96 h of incubation detected four known acids (citric, gluconic, malic and formic acid) along with three unknown acids. Molecular characterization showed our strain to be of Brevibacillus sp.

Application of an Expert System to Predict Maximum Explosive Charge Used Per Delay in Surface Mining

The present paper mainly deals with the prediction of maximum explosive charge used per delay (Q MAX) using an artificial neural network (ANN) incorporating peak particle velocity (PPV) and distance between blast face to monitoring point (D). One hundred and fifty blast vibration data sets were monitored at different vulnerable and strategic locations in and around major coal producing opencast coal mines in India. One hundred and twenty-four blast vibrations records were used for the training of the ANN model vis-a-vis to determine site constants of various conventional vibration predictors. The other 26 new randomly selected data sets were used to test, evaluate and compare the ANN prediction results with widely used conventional predictors. Results were compared based on coefficient of correlation (R), mean absolute error and mean squared between measured and predicted values of Q MAX. It was found that coefficient of correlation between measured and predicted Q MAX by ANN was 0.985, whereas it ranged from 0.316 to 0.762 by different conventional predictor equations. Mean absolute error and mean squared error was also very small by ANN, whereas it was very high for different conventional predictor equations.

Vibration characteristics of mining equipment used in Indian mines and their vibration hazard potential

Aims: This study aimed to monitor the vibration levels of mining machinery and duration of exposure to vibration; to study work practices of operators of mining machineries and to predict health risk from vibration exposure to operators. Materials and Methods: Vibration levels of 157 mining equipment including dumpers, dozers, etc. in 10 opencast mines were measured through accelerometer and recorded in vibration analyzer. Root mean square (RMS) values of acceleration as well as vibration dose values along with duration of exposures per day were used to predict health risk in accordance with ISO 2631-1:1997 standard. Video records of equipment operation were used to analyze job components. Results: Health risk was evaluated using RMS acceleration (0.21-1.82 m/s 2 ) and corresponding daily durations of exposure (2-7.5 h). Forty two (27%) of the equipment showed minimal health risk, 83 (53%) equipment showed moderate and 32 (20%) equipment showed high health risk to operators. While shovels and excavators showed minimal health risk, dozers and dumpers showed high health risk potential. x-axis was the dominant axis of vibration for loaders and dozers, whereas for the majority of dumpers and tippers, z-axis was dominant. Conclusion: Dumpers require engineering control for reducing the vibration in z-axis while measures are required for x-axis in loaders or dozers. Shovels or excavators do not require immediate attention except regular monitoring. Improvement in work practices are required to safeguard the workers from vibration related illness. It is recommended that proper guidelines for measurement and control of vibration at workplace should be formulated.

Blast-Induced Caving from Surface over Continuous Miner Panel at a 110m Cover in an Indian Mine

Continuous mining is a most popular mining method in USA and Europe. Nearly 60% of coal mining in the West is through continuous mining process in underground mines. Continuous miner technology, which has of late been introduced in India, is able to extract 65–74% of the coal in a panel depending upon the seam parameters as against 50–60% by semi-mechanized Bord and Pillar system of mining with SDL/LHDs, which is popular in India. The rate of extraction by the continuous miner being high is able to create larger panels, and thus, reduces the coal loss in barrier pillars. Presently, efforts are being made to introduce this technology on a larger scale in underground coal mines of Coal India Limited in India. When the first depillaring panel started its operation in November 2009 at Jhanjra, the panel was stopped after extraction of nine pillars by the Indian regulatory body (Directorate General of Mines Safety, DGMS, GOI) as the geological conditions of the overlying strata gave trouble of non-caving. The anticipated roof fall did not take place. The exposed roof area reached 10,400 m2, which was equivalent to 46,800 m3 of the void volume posing a threat of air blast. Since all the attempts to induce caving by underground blasting failed, an attempt was made from surface to induce the caving by destress blasting. This paper deals with the design of blasting parameters and execution of destress blasting keeping in view the safety and sentiments of nearby villages.

A New Blastability Index for Hard Roof Management in Blasting Gallery Method

The presence of hard and massive sandstone above the coal seam in underground coal mines often leads to delay in caving of overlying rock beds thereby causing excessive load on supports and posing danger to underground workings. The problem is more prominent in blasting gallery (BG) as well as longwall mining methods in Indian coal mines. Induced caving by blasting is a promising means for hard roof management in underground coal mines. Based on extensive studies and data collected from different mines in India, a Blastability Index (BI) has been developed which can be used for the classification of roof according to the degree of ease in caving by induced blasting. Different charge factors have also been suggested based on the Blastability Index. Due to wide change in the method of extractions, ‘Cavability Index’ for longwall panel was found ineffective in case of BG method of working as well as bord and pillar working. For this reason, this proposed Blastability Index would be of immense help for caving of hard roof by induced blasting.

The Shifting Gender of Coal: Feminist Musings on Women's Work in Indian Collieries

This paper investigates the sharp fall in the number of women workers in Indian coal mines, and explores the specificity of women workers in their demands for gender equity. It examines four main factors responsible for the gradual decline in women's participation in Indian collieries: the laws surrounding women's rights to work; the gendered impacts of technology use; the neglect of women workers' needs and interests by the relevant trade unions; and the gender discriminatory attitudes and instruments of the mining companies which have produced a certain kind of ideal worker who is also a gendered being. The paper asserts women's right to mine in order to earn a living, and to demand an equal share in the benefits that mining can offer.

A Study of Coal Mines in India

My hypothesis was coal industry in India traditionally backward due to transportation and lack of privatization. The point of lack of privatization is right because government started nationalize from 1972-1973. But as such my point of transportation I did not find any point. Coal has been recognized as the most important source of energy for electricity generation in India. About 75% of the coal in India is consumed in the power sector. In addition, other industries like steel, cement, fertilizers, chemicals, paper and thousands of medium and small-scale industries are also dependent on coal for their process and energy requirements. In the transport sector, though direct consumption of coal by the Railways is almost negligible on account of phasing out of steam locomotives, the energy requirement for electric traction is still dependent on coal converted into electric power.Coal has been a major contributor in providing energy security during the past century. But it is not a renewable resource, one day it will exhaust. It is possible that this pattern may change and there could be emphasis on uranium and thorium based power plants during the later part of the 21st century in addition to the emphasis on renewable energy sources.

Two stages of gold mineralization at Hutti mine, India

The Hutti gold mine is located in a high-angle, NNW–SSE-trending shear zone system, which hosts nine discrete auriferous shear zones (reefs). On a clockwise, retrograde PT path two separate stages of deformation/metamorphism (D2/M2 and D3/M3) occurred synchronous with two distinct stages of gold mineralization, both of which were associated with different fluid types. Stage 1 mineralization developed during D2/M2, where the amphibolite host rocks were altered by a metamorphic fluid with a \( {{\delta }^{{18}}}{{O}_{{{{H}_2}O}}} \)of 7.5–10.1 ‰, rich in K, S, As, and Au at pressure and temperature conditions of around 3 kbar and 530 + 20/−30°C, respectively. The stage 1 auriferous shear zones are enveloped by a zoned alteration consisting of a distal biotite–chlorite and proximal biotite–plagioclase assemblage. Subsequently, D2/M2 was overprinted by D3/M3 deformation and metamorphism at 300–400°C and <2 kbar that formed the stage 2 mineralization. The stage 2 mineralizing fluid which originated from outside the greenstone belt (δ18Ofluid of 3.2–6.8 ‰) was rich in Si, Au, and W. This mineralization stage is distinct by the emplacement of laminated quartz veins central to the shear zone, containing locally visible gold at concentrations of up to 1 kg Au/t. The laminated quartz veins are surrounded by a millimeter-scale chlorite2–K-feldspar alteration halo, which replaced the stage 1 biotite–plagioclase assemblage. The oxygen isotopic composition of the stage 2 fluid suggests a mixture of a magmatic fluid with an oxygen isotopic composition in the range of 6 to 10 ‰ and an isotopically light formation fluid that resulted from fluid–rock interaction in the greenstone pile. The two fluid fluxes at stages 1 and 2 both contributed to the overall gold mineralization; however, it was the second fluid pulse, which gave the Hutti mine its status as the largest gold mine in India. The metamorphic evolution was thereby important for the first stage, whereas the second stage was controlled by tectonism and intrusion of the high-heat production Yellagatti granite that re-established the fluid plumbing and mineralizing system.

Prediction of Safe Charge to Protect Surrounding Structures Using Support Vector Machine

The present paper mainly with deals the prediction of safe explosive charge used per delay (QMAX) using support vector machine (SVM) incorporating peak particle velocity (PPV) and distance between blast face to monitoring point (D). 150 blast vibration data sets were monitored at different vulnerable and strategic locations in and around a major coal producing opencast coal mines in India. 120 blast vibrations records were used for the training of the SVM model vis-a-vis to determine site constants of various conventional vibration predictors. Rest 30 new randomly selected data sets were used to compare the SVM prediction results with widely used conventional predictors. Results were compared based on coefficient of correlation (R) between measured and predicted values of safe charge of explosive used per delay (QMAX). It was found that coefficient of correlation between measured and predicted QMAX by SVM was 0.997, whereas it was ranging from 0.063 to 0.872 by different conventional predictor equations.

Safety in Indian Coal Mines – Where Do We Go from Here

The 20th century has experienced a considerable amount of success in coal mine safety in India. The mining industry has for many years focused on injury prevention at the workplace through procedures and training, and has achieved considerable success. However, the statistics on major accident events such as fatalities and reportable incidents has not shown the corresponding levels of improvement. In the area of major hazards control, the mining industry approach has emphasized mainly on past experiences and lessons learnt, while other high hazard industries such as the chemical process industry and oil and gas industry have taken system safety techniques to new highs. A literature review on quantitative analysis of mine safely studies revealed that numerous investigators explored a wide- range of techniques, including the investigation of bivariate and multivariate statistical models. It is inferred that the use of these quantitative techniques can provide a new direction of research in mine-safety studies. The important aspect, which was explored in this study through structural equation modeling, is the sequential interrelationships amongst the personal, social, and technical factors leading to accident/injury causation. Interestingly, the accidentinvolved workers are more job stressed, more job dissatisfied and hence, less job involved and often get bored with their jobs. The level of dissatisfaction in mines is quite expected. Further research should be performed using national data set so that the findings can be generalized to all segments of the mining industry. Keywords - Mine Safety, Quantitative Risk Analysis, Structural Equation Modeling, Personal, Social and Technical Factors

Numerical modelling of two stoping methods in two Indian mines using degradation of c and mobilization of φ based on Q-parameters

Two Indian mines are the subject of a comparative study of a strain-softened Hoek–Brown and FLAC 3D modelling, and a novel ‘ c then tan φ’ strain-softening-strain-mobilization approach, using Q-system based input data. This approach is also used with FLAC 3D, using identical stope geometries. The parameters CC and FC, denoting the cohesive component and frictional component of shear strength, are extracted directly from the Q-logging and knowledge of UCS, and are the source of the peak values. Measured deformations, or the strains recorded over the total length of pre-mining installed MPBX, are compared and effectively calibrate the models, in view of the very similar deformations obtained from empirical formulations based on Q using the competence factor approach, as in SRF. The ‘ c then tan φ’ approach appears to give the most realistic match to observations in the mines, including the modelling of a shear band within the back or roof of a stope, rather than at the surface of the stope. The Q-based approach also uses a depth-dependent modulus, and this is perhaps the reason why the strain-softened Hoek–Brown model, without this stiffening with depth, shows ‘global failure’ in a second mine having a wider range of depths within one model, and many openings, since modulus is not increased in standard-method approaches.

Cardiac workload of dressers in underground manual coal mines

Introduction: Occupational disorders invite absenteeism amongst the miners. Though rapid technological advancement has happened, yet assessment of cardiac workload was largely ignored in underground coal mines in India. Methods: Physiological stress was evaluated in terms of working heart rate, net cardiac cost and relative cardiac cost. Heart rate was measured during their course of work by heart rate monitor at the coal face. Recovery heart rates and environmental heat load were also assessed. Results: Heart rate was found to be 117 and 122 beats/min respectively in first and second spell. NCC (49.7 and 54.8 beats /min) and RCC (47% and 52%) exhibit significant variations between spells, whereas rate of recovery had been very poor amongst the workers who regularly exceeded recommended levels of cardiac strain indices. The nature of work depicted it as a heavy job although recovery trend categorizes it heavier than that. ET and WBGT were above the recommended limits as per the guidelines of WHO and ACGIH. Conclusions: High physiological demand of the job with towering heat stress was found to hinder the recovery process and may cause deleterious impacts on the workers. Ergonomic interventions were highly felt towards job organization and up gradation of environmental conditions. Keywords: Coalmines; dressers; workload DOI: http://dx.doi.org/10.3126/joim.v32i2.4938 Journal of Institute of Medicine, August, 2010; 32: 11-17

Development of Statistical Model for Prediction of Occupational Noise Exposure to SDL Operators in Indian Underground Coal Mines

The main aim of this paper is to assess present scenarios of occupational noise exposure of the operators of a popular category of SDL in Indian underground coal mines and to develop a statistical model for prediction of occupational noise exposure to the SDL operators using machine age as an independent variable. Eighty SDL machines were selected randomly from 18 different mines. Machines working hour were monitored and recorded for all 18 mines. Full shift noise dose (TWA) was measured for the operator of each machine. Regression analysis was performed to develop the statistical model. Validity of the model was verified. The subjects are exposed to occupational noise ranging from 74 to 100.4 dBA TWA. The operator's TWA increases with increase in machine age. A fifth order polynomial equation describes the relationship between machine age and TWA. In a validation study, it was found that the predictive model works in the field on similar machines. The SDL operators are exposed to occupational noise generated, which ranges from 74 to 100.4 dBA TWA. The TWA increases with increase in the machine age. There exists a non linear relation between the SDL age and the corresponding TWA. The predictive statistical model developed in this study works satisfactorily in the field, hence the same is recommended for selected class of SDL machines deployed in Indian underground coal mines.

Use of spacer aided initiation technique in solid blasting in Indian underground coal mines

Solid blasting mining methods contribute about 60% of total underground coal production in India. Spacer aided initiation technique utilises the inherent air gap sensitivity of the explosive to distribute the blast energy over a longer length by the use of air decking using plastic spacers with single priming to achieve higher pull in solid blasting. The results of exploratory field trials of the use of spacer aided initiation technique in solid blasting with a specially developed Pentadyne‐HP explosive conducted in an underground mine concluded that it was possible to achieve a pull of up to 2·2 m and yield up to 41 t per blast in a development face. Based on results of the studies conducted by authors, statutory authority for mines safety in India granted approval for commercial use of this technique with Pentadyne‐HP explosive in all the degree I gassy underground coal mines.

Occupational health assessment of chromite toxicity among Indian miners.

Elevated concentration of hexavalent chromium pollution and contamination has contributed a major health hazard affecting more than 2 lakh mine workers and inhabitants residing in the Sukinda chromite mine of Odisha, India. Despite people suffering from several forms of ill health, physical and mental deformities, constant exposure to toxic wastes and chronic diseases as a result of chromite mining, there is a tragic gap in the availability of 'scientific’ studies and data on the health hazards of mining in India. Occupational Safety and Health Administration, Odisha State Pollution Control Board and the Odisha Voluntary Health Association data were used to compile the possible occupational health hazards, hexavalent chromium exposure and diseases among Sukinda chromite mines workers. Studies were reviewed to determine the routes of exposure and possible mechanism of chromium induced carcinogenicity among the workers. Our studies suggest all forms of hexavalent chromium are regarded as carcinogenic to workers however the most important routes of occupational exposure to Cr (VI) are inhalation and dermal contact. This review article outlines the physical, chemical, biological and psychosocial occupational health hazards of chromite mining and associated metallurgical processes to monitor the mining environment as well as the miners exposed to these toxicants to foster a safe work environment. The authors anticipate that the outcome of this manuscript will have an impact on Indian chromite mining industry that will subsequently bring about improvements in work conditions, develop intervention experiments in occupational health and safety programs.