Indian Coal Mines Research Articles

Study of efficiency and productivity growth in opencast and underground coal mining in India: a DEA analysis

This paper attempts to study efficiency and productivity of coal mining in the Indian coal sector using detailed input and output data for underground and opencast coal mining for the period between 1985 and 1997. The non-parametric approach of data envelopment analysis (DEA) is adopted for performance analysis of different coal mining regions. Total factor productivity growth was analysed using the Malmquist index by decomposing productivity change into efficiency and technical change. Results of the analysis do not conform to the prevailing notion of opencast (OC) mining having shown more productivity growth than underground mining in India. An increasing percentage of OC mining regions showed a decline in efficiency over the period of analysis. Approximately 58%, 59% and 67% of the mining regions showed decline in productivity between 1985 and 1990, 1990 and 1995 and 1995 and 1997, respectively. Technical progress seems to have been the major driving factor behind productivity growth in opencast mining, while efficiency growth has been the most important factor in growth of underground mine productivity. Underground mines seem to have adopted a more efficient practice of operation to compensate for the lag in technical change. On the other hand, operational efficiency of opencast mines seems to have been overlooked in the process of increasing production through technological improvement in OC mining.

Numerical estimation of pillar strength in coal mines

Results of numerical modelling of failed and stable cases of pillars from Indian coal mines are reported in this paper. The complete procedure for modelling using FLAC 3D in the strain-softening mode is given. It is shown that estimation of pillar strength is possible using numerical modelling and it may provide a viable, and perhaps better, alternative to earlier conventional pillar strength approaches. Methods are given to estimate the large number of input parameters required in the models. Because of the paucity of rock characterisation and in situ stress data, some approximations and assumptions were made in all the cases based on earlier experience. The modelling work leads to the conclusion that such data are necessary for the success of this method. Areas for further research related to this subject are given in the end.

Segregation of coal by single–shot blasting of composite strata in opencast mines

Good-quality coking coal occurring at shallow depths was worked extensively in the early days of coal mining in India, but in combination with the propensity of the seams to spontaneous heating this unplanned mining has made fires a threat to most of the mines of the Jharia coalfields. Lakshmi opencast mine of the Bhowra Area of Bharat Coking Coal Limited (BCCL), a subsidiary of Coal India Limited (CIL), fell victim to such ill-organized private operations and had to be excavated to protect existing mines and other important structures that surround the fire area.

Prediction of air pollution from a proposed opencast coal mine

Industrialization, urbanization and motor traffic are increasing rapidly in developing countries. The consequent air pollution problems are serious1 owing to the absence of the kind of control imposed on emissions in the developed world. In India a tremendous increase in opencast mining in recent years2 has drastically disturbed the air, water and land environments.3 Plants that grow in a polluted environment accumulate trace elements at high concentrations, causing a serious risk to human health when plant-based foodstuffs are consumed,4–7 and the survival of forests is threatened.8 Such activities as drilling, blasting, loading and unloading, transportation of minerals and wastes, etc., make opencast mining a major source of air pollution. A detailed study of emission sources and quantification of the concentration of pollutants together with modelling to predict air pollution levels are essential to the preparation of an environmental impact assessment of any proposed opencast mining project.9,10 If high, the predicted levels of air pollution need to become the basis of an effective management plan.11,12 An attempt is made here to predict the air pollution from a proposed opencast coal mine in India, including determination of the emission rates from different mining activities, and to design effective long-term control measures.

Observations and classification of roof strata behaviour over longwall coal mining panels in India

Abstract A study has been made of a number of mechanized longwall panels in various coal mines in India, concentrating on the geology, physico-mechanical rock properties and the behaviour of the coal measure roof rocks during mining. The research has highlighted the splitting and caving characteristics of the strata rocks and enabled the development of a roof-rock classification system. Roof rocks are classified into six categories based on the: (a) mean weighted uniaxial compressive strength; (b) RQD; (c) (i) type of rocks, (ii) presence of cracks, fissile beds, splitting, etc., (iii) presence of water; and (d) thickness of bed layer. The behaviour of layers and composite layers in the immediate roof rock mass is also enumerated. Relations between the rock strength properties and values for the bulking factor of the failed rock are included. The concepts of a ‘weighting zone’ and ‘caving zone’ are proposed. The paper also clarifies the occurrence of different types of failure, such as periodic falls. All these findings should be helpful during calculation of the powered support capacity.

The Analysis of Fatal Accidents in Indian Coal Mines

This paper describes the analysis of fatal incidents of Indian coal mines from April 1989 to March 1998. It is found that Indian mines have considerably higher accident and fatality rates compared to those in USA and South Africa, respectively. While open cast mines are generally known to be safer than underground mines, the Indian open cast mines are shown to be at least as hazardous to the workers as the Indian underground mines. Analysis of the accident rates is made via a few regression models involving the effects of working shifts, the various companies, the types of mine, manshift and production. The accident-prone combinations of mine type and company are identified for follow-up action. The break-up of the accidents by cause is also studied. AMS (2000) Subject Classification: Primary 62-07; Secondary 62P99, 62N05.

The use of air decks in production blasting in an open pit coal mine

The influence of air deck blasting on blast performance and blast economics and its feasibility has been studied in the production blasting of soft and medium strength sandstone overburden rocks in an open pit coal mine in India. The air deck blasting technique was very effective in soft and medium strength rocks. Its main effects resulted in reducing fines, in producing more uniform fragmentation and in improving blast economics. The fines were reduced by 60–70% in homogeneous sandstones. Oversize boulders were reduced by 80% and shovel loading efficiency was improved by 20–40% in blocky sandstones. The explosive cost was reduced by 10–35% dependent on the type of rock mass. Throw, backbreak and ground vibration were reduced by 10–35%, 50–80% and 30–94% respectively. For a particular rock mass and blast design environment, air deck length (ADL) significantly influenced the fragmentation. ADL as represented by air deck factor (ADF) in the range of 0.10–0.35 times the original charge length (OCL) produced optimum results. ADF beyond 0.35 resulted in poor fragmentation and in inadequate burden movement.

Evaluation of Risk of Occupational Injuries Among Underground Coal Mine Workers Through Multinomial Logit Analysis

The purpose of this study was to assess the risk of injuries to miners, accounting for their individual and workplace characteristics. The binary and multinomial logit models were applied to measure the risk of injuries to miners working in a group of underground coal mines in India. The binary logit model measures the risk of injuries to the miners; whereas, the multinomial logit model measures the risk of severe and reportable injuries. The study revealed that both the individual and workplace characteristics of the miners have significant effect on the risk of occurrence of injuries. Of the individual variables, while the age and experience of the miners do not have any significant effect on the risk of occurrence of injuries, the occupation categories show that the face workers are more risky in the occurrence of an injury. Among the workplace variables, the workplace location categories show that the outby-face location is more accident prone.

Coal mining in India and US sanctions: A reply to Simon walker

Abstract Simon Walker notes that even without nuclear sanctions the Indian coal sector would still not represent a favourable location for private‐sector investment.1 He states that the sanctions may have added to the problem of attracting foreign investors, but that the Indian Government should have taken this into consideration before it launched its series of nuclear tests. On receipt of Walker's comments, particularly on the bureaucratic attitude to liberalization of the coal sector, field investigations were conducted to try to reach the root causes of private sector failures to rise to the occasion when the opportunity presented itself to enter the industry (hitherto reserved for the public sector). The findings more or less concur with the observations of Walker, except that funds expected from resources abroad might have acted as a catalyst in helping the private sector to overcome the bureaucratically erected hurdles. Walker's views on nuclear sanctions are more alarming, however. The economic sa...

Coal mining in India and US sanctions: A comment on G.D. Kalra

Abstract In an earlier issue of the journal G.D. Kalra commented on the coal mining sector of India in the post US sanctions period. He noted in particular that the infant private sector is in need of funds from abroad in their capital intensive coal mining ventures. However, the US sanctions following the nuclear device testing period, have failed these investments. The following comment by Simon Walker challenges this view, and notes that even with no sanctions the Indian coal sector would not represent a favourable location for private‐sector investment. In addition, the sanctions may have added to the problem of attracting foreign investors, but that is something that the Indian Government should have taken into consideration before it launched its series of nuclear tests.

Coal mining in India in the post US sanctions period

Abstract US sanctions against India in the post-nuclear device testing period, has affected many sectors of the Indian economy. This comment focuses on the impacts on the coal mining industry in the country. It is very recently that the coal industry has been deregulated allowing private sector participation. The infant private sector was looking towards the flow of funds from abroad in their capital intensive coal mining ventures. Basically, the US sanctions have failed them.

97/02380 Respirable dust characterization in an Indian open-cast coal mine

97/02380 Respirable dust characterization in an Indian open-cast coal mine

Respirable Dust Characterization in an Indian Open-Cast Coal Mine

Abstract There has been a phenomenal increase in the production of coal from surface mines in India. Vehicular traffic on haul roads of mechanized open-cast coal mines has been identified as the most prolific source of fugitive dust. The airborne dust not only creates a serious health hazard, but also affects the productivity through poor visibility and increased maintenance cost and ultimately deteriorates the ambient air quality in and around the mining sites. An intensive study was carried out in the Muraidih Open-cast Project of Bharat Coking Coal Ltd. (Dhanbad, Bihar, India) for 1 year to characterize the airborne haul road dust. The percentage of suspended particulate matter at the various size ranges and the free silica content of each of the size ranges of haul road dust were determined. Dust particles are an obvious source of trace elements in the mines. Concentrations of nine trace elements in the haul road dust and the benzene-soluble fractions of suspended particulate matter at the various sta...

Blasting side effects - Investigations in an opencast coal mine in India

ABSTRACT Field investigations were conducted in a potential opencast coal mine in India with a view to optimizing blast patterns for controlling ground vibration, sound pressure level and fly rock within safe and tolerable limits. Blasting was performed in all operating benches i.e., alluvium, sandstone, shale, coal and blast vibrations were monitored on the alluvial soil present in the vicinity of the mine. It was observed that in all the blasting rounds, low frequency ground vibrations were generated. Further investigations were carried out by recording structural response to ground vibration on single and double storied buildings. It was observed that the ground vibrations were amplified by structures themselves, as much as 2.0 to 5.6 times

Case studies in coal mines in India : A.H. Wilson, Comprehensive rock engineering. Vol. 5, ed J.A. Hudson, (Pergamon), 1993, pp 447–522

Case studies in coal mines in India : A.H. Wilson, Comprehensive rock engineering. Vol. 5, ed J.A. Hudson, (Pergamon), 1993, pp 447–522

Bumps and rockbursts in Indian coal mines — an overview : Ghose, A K In: ROCKBURSTS, Global Experiences (Paper to the 5th Plenary Scientific Session of Working Group on Rockbursts of International Bureau of Strata Mechanics, Hyderabad, 2–3 February 1988)P123–129. Publ Rotterdam: A A Balkema, 1990

Bumps and rockbursts in Indian coal mines — an overview : Ghose, A K In: ROCKBURSTS, Global Experiences (Paper to the 5th Plenary Scientific Session of Working Group on Rockbursts of International Bureau of Strata Mechanics, Hyderabad, 2–3 February 1988)P123–129. Publ Rotterdam: A A Balkema, 1990

High-speed shaft sinking and outfitting techniques in Indian coal mines : Rao, Y R Colliery GuardV239, N5, July 1991, P134–138

High-speed shaft sinking and outfitting techniques in Indian coal mines : Rao, Y R Colliery GuardV239, N5, July 1991, P134–138

Strata control problems in and around fault planes of Central India coal basins : J Min Metal Fuels V38, N10/11, Oct–Nov 1990, P280–289

Strata control problems in underground coal mining account for highest fatal and serious injuries to workers. These problems are due to operational, geological and geo-technic parameters. Efforts are being made in various Indian coal mines to replace conventional timber supports by boltings, stitchings, hydraulic/friction props, chocks and shield supports for safety. Operation in and around faulted zones in Kamptee and Kanhan coalfield of Central India posed most serious challenge to safety of miners. Evaluation of orientation, throw and frequency of faults along with cleats and joints were studied with a view to evolving safe and economic system of supports and method of mining. Faults are the main geo-structural features disturbing bord and pillar and longwall workings. The fault throw up to the working height could be tackled without major change in layout and hence were called small throw faults. Over 20faults of throw within a metre to 60 m were observed in depth for gouge thickness and associated strata control problems. Faults with 10 m throw and above in creased face cleat and mjor joint frequency from 11m-1 to 16 m-1 and above and 4 m-1 to 10 m-1reswpectively within 5 to 50 m of its position. Orientation of face cleat and major joint west was also influenced by such faults which were classified as major faults. Entries along the major and the minor faults suffered from severe strata control problems. For better roof condition, drivages shouid be laid 20-45° across the faults; reinforcement of supports by way of stitchings and use of M.S. cross-bars along with conventional supports should be installed immediately in the faulted zones to avoid deterioration of exposed strata.

Inhibition of mild steel corrosion in acid mine waters containing ferric ions

AbstractCorrosion of underground mining equipment by acid mine waters in some north eastern Indian coal mines can be quite serious. It has been found that the presence of Fe3+ (concentration levels up to 500 mg l−1) in acid mine waters is mainly responsible for rapid corrosion of mild steel through its reduction to Fe2+. Microbial aspects of Fe3+ generation in acid mine waters are also considered. Inhibition of the corrosion of mild steel in synthetic as well as original acid mine waters containing Fe3+ has been investigated from the aspect of the chemical species (complexes, compounds) formed with Fe2+ and Fe3+. The results of this investigation show that not all the inhibitors which gave acceptable protection to mild steel in sulphuric acid solutions were successful in acid mine waters containing Fe3+. Complete protection of mild steel was achieved with chromate, oxalate, and gluconate while quaternary ammonium compounds, thiourea, diaminoacetyl thiourea, and amines offered fair inhibition. Scanning ele...

Geomechanics classification for support selection in Indian coal mines — case studies : Sinha, A; Venkateswarlu, V Proc 5th International Congress International Association of Engineering Geology, Buenos Aires, 20–25 October 1986V1, P159–164. Publ Rotterdam: A A Balkema, 1986

Geomechanics classification for support selection in Indian coal mines — case studies : Sinha, A; Venkateswarlu, V Proc 5th International Congress International Association of Engineering Geology, Buenos Aires, 20–25 October 1986V1, P159–164. Publ Rotterdam: A A Balkema, 1986