The Experts below are selected from a list of 1347 Experts worldwide ranked by ideXlab platform
G. H. Lind - One of the best experts on this subject based on the ideXlab platform.
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An integrated risk management approach for underground coal Pillar Extraction in South Africa
Journal of The South African Institute of Mining and Metallurgy, 2005Co-Authors: G. H. LindAbstract:Analysis for Pillar Extraction potential (A-PEP) is an intelligent tool, which could be used as a preliminary output indicator when considering the secondary Extraction of regional support Pillars in the Witbank and Highveld coalfields of South Africa. The safe and economic Extraction of underground coal Pillars is of paramount significance and importance to the South African coalmining industry to ensure continuity of supply of this fossil fuel. Pillar Extraction practices in South Africa have been responsible a significant proportion of safety and fatality statistics in relation to its relative output (less than 5 per cent of total South African coal production) and, as a result, research was undertaken in local Pillar Extraction operations and extended to similar operations in New South Wales, Australia to assess a way forward for Pillar Extraction in South Africa. It was found that, although little in the way of new technologies has emerged in this field in the recent past, significant contributions could be made in the field of risk analysis to obtain a generic design methodology for Pillar Extraction in South Africa. The resultant A-PEP tool to assess Pillar Extraction potential is based on certain physical, risk and economic factors, which combine to indicate operational success in terms of economic, health and safety attributes. At the time of A-PEPi?½s development there was a lack of operating underground coal Pillar Extraction operations, which made it difficult to validate its applicability. Since then, however, A-PEP has been successfully tested and validated against two unique underground coal Pillar operations, which is the discussion of this paper. One operation is situated in the Witbank coalfield and is extracting Pillars, which are 20 years old and at a depth of 80 metres below surface, while the other operation is situated in the Highveld coalfield-which is extracting 6 month-oldPillars underneath a massive dolerite sill at a depth of 220 metres. A-PEP has shown that its predictive nature is consistent the workings at both operations, irrespective of their unique conditions, and as such it can be successfully used as a mine planning tool. The A-PEP mine planning tool thus represents a positive step toward an integrated approach to underground coal Pillar Extraction when considering legal and operational aspects, which could form the basis for legislative guidelines when considering the future of Pillar Extraction in South Africa.
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Risk management of underground coal Pillar Extraction in South Africa
International Journal of Surface Mining Reclamation and Environment, 2005Co-Authors: G. H. LindAbstract:Analysis of Pillar Extraction Potential (A-PEP) is an intelligent tool that could be used as a preliminary output indicator when considering the secondary Extraction of regional support Pillars in the Witbank and Highveld coalfields of South Africa. Pillar Extraction practices in South Africa have consumed a significant proportion of safety and fatality statistics in relation to its relative output (less than 5% of total South African coal production) and as a result research was undertaken in local Pillar Extraction operations and extended to similar operations in New South Wales, Australia to assess a way forward for Pillar Extraction in South Africa. The A-PEP tool is based on certain physical, risk and economic factors that combine to be indicative of operational success in terms of economic, health and safety attributes. In this paper it is successfully tested against two existing Pillar Extraction operations.
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Mitigating the risks associated with underground coal Pillar Extraction in South Africa
Mining Technology, 2004Co-Authors: G. H. LindAbstract:AbstractThe safe and economic Extraction of underground coal Pillars is of paramount significance and importance to the South African coal mining industry. Research was undertaken into local Pillar Extraction operations and extended to similar operations in New South Wales, Australia to assess the way forward for Pillar Extraction in South Africa. It was found that although little in the way of new technologies has emerged in this field in the recent past in South Africa, significant contributions can be made in the field of risk analysis to obtain a generic design methodology for Pillar Extraction. For example, a Pillar Extraction planning tool was developed (A-PEP) to assess Pillar Extraction potential based on certain physical, risk and economic factors. A-PEP is an intelligent tool which can be used as a preliminary output indicator before more in-depth investigations into the future use of Pillar Extraction are warranted. The design methodology and planning tool presented here (which has significant ...
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Coal Pillar Extraction experiences in New South Wales
Journal of The South African Institute of Mining and Metallurgy, 2002Co-Authors: G. H. LindAbstract:New South Wales has a successful history of Pillar Extraction stretching back more than 60 years. Various methods of Pillar Extraction ranging from the rib Pillar methods (such as the Wongawilli system) to the more recent Pillar stripping techniques (similar to those used in the USA) are discussed in this paper. These discussions are based on the experiences of the author stemming from a recent research tour of seven underground Pillar Extraction operations in New South Wales as part of the Coaltech 2020 collaborative research initiative. Some operational issues of each site visited are presented before some general comments pertaining to the overall success of Pillar Extraction in New South Wales are discussed. Generally Pillar Extraction in New South Wales is on the decline in favour of longwalling. However, the Pillar Extraction that is conducted is done so along specific guidelines to ensure their success, and these are also discussed.
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Key success elements of coal Pillar Extraction in New South Wales
Journal of The South African Institute of Mining and Metallurgy, 2002Co-Authors: G. H. LindAbstract:Seven full and partial Pillar Extraction operations were visited in New South Wales, Australia, in the early parts of 2001. Certain factors unique to these operations have led to the general success of the safe and economic Extraction of these coal Pillars. Some of these factors attributable to the overall success of these operations are discussed in this paper. In particular, geotechnical mapping, specific legislation pertaining to Pillar Extraction, mining methods, the role of temporary supports and training are descriptionbed. It is found that some of these factors have useful attributes which could be used to design a methodology for Extraction of underground coal Pillars in the Witbank and Highveld coalfields of South Africa.
Rajendra Singh - One of the best experts on this subject based on the ideXlab platform.
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Coal Pillar Extraction Under Weak Roof
Mining Metallurgy & Exploration, 2020Co-Authors: Arun Kumar Singh, Rajendra Singh, Rakesh Kumar, Ashok Kumar, Dheeraj Kumar, Sahendra Ram, Amit Kumar SinghAbstract:This article offers an examination of a retreat mining method conducted at the Pinoura Mine in India from 2010 to 2017. The method is atypical for coal mines of India’s coalfields. The method executes dePillaring in a single pass and does not require the formation of galleries and support installation in splits, thus, reducing the cycle time. A variety of observations are discussed throughout this work and emphasis is placed on field measurements and dePillaring under weak roof ( RMR = 40–45). This paper discusses design techniques, specifically the estimation of the snook (remnant Pillar) size, and important practical observations after the fact. The execution of this method was eventually conducted in eleven panels.
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Roof sagging limit in an early warning system for safe coal Pillar Extraction
International Journal of Rock Mechanics and Mining Sciences, 2019Co-Authors: Ashok Kumar, Rajendra Singh, Arun Singh, Rakesh Kumar, Dheeraj Kumar, Sahendra Ram, Abhishek Gautam, Amit Kumar SinghAbstract:Abstract Field studies have found that, generally, a roof fall takes place after certain amount of roof strata sagging. Recent applications of auto warning tell-tale (AWTT) instrument as an early warning system at different dePillaring panels found it to be simple, economical and efficient during the coal Pillar Extraction (called dePillaring). AWTT is able to watch the set value of roof sagging continuously in time. However, the application of AWTT experienced two practical issues: (i) fixing roof sagging warning value before the fall of overlying strata and (ii) deciding horizon above which its anchorage point of AWTT needs to be installed. Different field experiences noticed that an anchorage horizon at 10 m depth from the ceiling of a gallery works satisfactorily for goaf edge. But fixation of the roof sagging warning value, before the fall of overlying strata, is found to be complex. Generally, the warning value for a given site conditions is determined by extensive field monitoring and correlation of the roof sagging value at the goaf edge with corresponding roof falls. Field studies found that modulus of elasticity and thicknesses of immediate roof are important parameters in deciding the warning value of the roof sagging. These studies also indicated that the variation in size of the left-out ribs and goaf span influence the warning value. These observed facts about the warning value for an AWTT are studied in laboratory using a numerical modelling approach in FLAC3D. The results obtained through developed simulated models are found to be in close agreement with those of the field studies. Attempts are also made to quantify the influence of above-mentioned parameters over the warning value through collated results of different studied models. The obtained results of field and laboratory investigations are presented and discussed in this paper for strata control in a dePillaring panel.
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Coal Pillar Extraction at deep cover: With special reference to Indian coalfields
International Journal of Coal Geology, 2011Co-Authors: Rajendra Singh, Prabhat Kumar Mandal, Arun Singh, Rakesh Kumar, Amalendu SinhaAbstract:Majority of the developed Indian coal seams are lying under strong and massive overlying strata. Depth of cover of these coal seams, standing on Pillars, varies from 50 to 500 m. Present Pillar Extraction (dePillaring) practises of the country have, predominantly, adopted intermediate mechanisation along with few fully mechanised dePillaring faces. Most of these faces are operating at shallow cover. But the existing techno-economical conditions of the industry are attracting a fully mechanised dePillaring system for deep seated coal Pillars, which is likely to grow in near future. Here the circumstances of bord and Pillar mining are to face difficult surroundings, mainly, due to rock-mass characteristics and stress conditions of the deep horizon. Although these two parameters are difficult to be pre-assessed accurately, a couple of recent experiences of dePillaring at deep cover have shown their influence over efficiency and safety of the dePillaring. A review of Pillar Extraction practises of other coal producing countries, under varying geo-mining conditions, showed importance of these parameters for the dePillaring. Providing a brief review of underground coal Pillar Extraction scenario, this paper presents geo-technical challenges encountered during caving of massive roof strata at two deep Indian dePillaring faces. These two trials experienced problems of (a) roof instability (b) barrier Pillar instability and (c) Pillar-spalling/floor-heaving. In absence of an effective hard roof management approach these problems could simply be dealt, up to some extent, by improvement in competency of the natural support.
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An observational approach for assessment of dynamic loading during underground coal Pillar Extraction
International Journal of Rock Mechanics and Mining Sciences, 2011Co-Authors: Rajendra Singh, Prabhat Kumar Mandal, Aastha Singh, Jhareswar Maiti, Rashmi Singh, Rakesh KumarAbstract:On the basis of a large number of field investigations, in and around underground coal mining faces (bord and Pillar) in India, this paper discusses issues of measurement and analysis of strata control parameters. Requirement of different types of instruments along with their suitability to monitor the strata control parameters under varying geo-mining conditions of the existing coal mines is also briefly explained. On the basis of field experiences, it is observed that the type of instrument to be placed in and around a dePillaring face is more or less dependent upon the geo-mining conditions of the site. Field investigations showed that the continuous monitoring (in time) of these instruments, preferably with the help of a data-logger, can provide important information about performance of mining structures (bord and Pillar) during caving of a competent overlying roof stratum. However, in absence of a data-logger, a simple process: called as Combined-Instruments-Approach (CIA) is implemented for some improvement in visualization of overlying strata behavior through manually observed data of the instruments. Scope of application of this approach to anticipate caving behavior of strong and massive roof strata during conventional dePillaring practice is demonstrated through analysis of an actual field monitoring results.
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Rock Mechanics challenges of dePillaring at deep cover
2009Co-Authors: Arun Kumar Singh, Rajendra Singh, Prabhat Kumar Mandal, Rakesh Kumar, Amit Kumar Singh, Sahendra RamAbstract:Underground coal mining at deeper cover encounters difficult underground environment due to increase in gas content and rise in temperature transition of a mining practice from shallow to high depth cover encounters a big change in the rock mass characteristics and the stress condition becomes more complex. At higher depth of cover, the excavation starts encountering stress control regime rather than structural control behavior of the rock mass. Mechanisation and automation of underground mining activities is a solution to improve the performance of deeper mines but the approach should match with the rock mass and stress conditions of the site. Since inception, CIMFR (formerly, CMRI) is continuously working to understand behavior of the rock mass through laboratory testing, field investigations and study on simulated models. Obtained experiences during these investigations are observed to be of strategic importance during application of a modern technology to improve practical mining conditions. This paper reviews rock mechanics aspects of different mechanized Pillar Extraction approaches during mining of a deep seated coal seam and, also attempts to present an appraisal of some of the recent technical developments to overcome the challenges of a deep underground coal mining.
Prabhat Kumar Mandal - One of the best experts on this subject based on the ideXlab platform.
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Role of geological discontinuities during application of continuous miner technology in underground coal mines
2016Co-Authors: A. Kushwaha, Rana Bhattacharjee, Subhashish Tewari, Prabhat Kumar MandalAbstract:A major portion of ground control problems encountered in underground coal mines can be attributed to geological discontinuities in the coal seam and the strata surrounding the seam. The role of geological discontinuities becomes more vital during application of mass production technology like continuous miner in maintaining safety, production and efficiency. Careful and detailed geological mapping to pick up the trend of joints, faults/slips, cleat etc., and documentation of roof instability problems encountered during development is essential in anticipating and controlling instability in the mine roof before planning of Pillar Extraction. Mapping helps in planning the orientation of Extraction line to induce caving during dePillaring and improving stability at the face significantly. Loss or damage of machines including decrease in production and productivity due to trapping of continuous miner may also be avoided. This technique estimates the orientation of major principal stress and avoids heavy expenditure on conducting in-situ stress measurements. It enhances in understanding the influence of drivage direction on roadway conditions and re-orientation of the roadways to attain stability in the roof. In the present paper, authors have dealt two cases, VK-7 incline and GDK-II incline mines of Singareni Collieries Company Limited (SCCL), where geological discontinuities played a crucial role during application of continuous miner technology in underground coal mines.
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Coal Pillar Extraction at deep cover: With special reference to Indian coalfields
International Journal of Coal Geology, 2011Co-Authors: Rajendra Singh, Prabhat Kumar Mandal, Arun Singh, Rakesh Kumar, Amalendu SinhaAbstract:Majority of the developed Indian coal seams are lying under strong and massive overlying strata. Depth of cover of these coal seams, standing on Pillars, varies from 50 to 500 m. Present Pillar Extraction (dePillaring) practises of the country have, predominantly, adopted intermediate mechanisation along with few fully mechanised dePillaring faces. Most of these faces are operating at shallow cover. But the existing techno-economical conditions of the industry are attracting a fully mechanised dePillaring system for deep seated coal Pillars, which is likely to grow in near future. Here the circumstances of bord and Pillar mining are to face difficult surroundings, mainly, due to rock-mass characteristics and stress conditions of the deep horizon. Although these two parameters are difficult to be pre-assessed accurately, a couple of recent experiences of dePillaring at deep cover have shown their influence over efficiency and safety of the dePillaring. A review of Pillar Extraction practises of other coal producing countries, under varying geo-mining conditions, showed importance of these parameters for the dePillaring. Providing a brief review of underground coal Pillar Extraction scenario, this paper presents geo-technical challenges encountered during caving of massive roof strata at two deep Indian dePillaring faces. These two trials experienced problems of (a) roof instability (b) barrier Pillar instability and (c) Pillar-spalling/floor-heaving. In absence of an effective hard roof management approach these problems could simply be dealt, up to some extent, by improvement in competency of the natural support.
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An observational approach for assessment of dynamic loading during underground coal Pillar Extraction
International Journal of Rock Mechanics and Mining Sciences, 2011Co-Authors: Rajendra Singh, Prabhat Kumar Mandal, Aastha Singh, Jhareswar Maiti, Rashmi Singh, Rakesh KumarAbstract:On the basis of a large number of field investigations, in and around underground coal mining faces (bord and Pillar) in India, this paper discusses issues of measurement and analysis of strata control parameters. Requirement of different types of instruments along with their suitability to monitor the strata control parameters under varying geo-mining conditions of the existing coal mines is also briefly explained. On the basis of field experiences, it is observed that the type of instrument to be placed in and around a dePillaring face is more or less dependent upon the geo-mining conditions of the site. Field investigations showed that the continuous monitoring (in time) of these instruments, preferably with the help of a data-logger, can provide important information about performance of mining structures (bord and Pillar) during caving of a competent overlying roof stratum. However, in absence of a data-logger, a simple process: called as Combined-Instruments-Approach (CIA) is implemented for some improvement in visualization of overlying strata behavior through manually observed data of the instruments. Scope of application of this approach to anticipate caving behavior of strong and massive roof strata during conventional dePillaring practice is demonstrated through analysis of an actual field monitoring results.
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Rock Mechanics challenges of dePillaring at deep cover
2009Co-Authors: Arun Kumar Singh, Rajendra Singh, Prabhat Kumar Mandal, Rakesh Kumar, Amit Kumar Singh, Sahendra RamAbstract:Underground coal mining at deeper cover encounters difficult underground environment due to increase in gas content and rise in temperature transition of a mining practice from shallow to high depth cover encounters a big change in the rock mass characteristics and the stress condition becomes more complex. At higher depth of cover, the excavation starts encountering stress control regime rather than structural control behavior of the rock mass. Mechanisation and automation of underground mining activities is a solution to improve the performance of deeper mines but the approach should match with the rock mass and stress conditions of the site. Since inception, CIMFR (formerly, CMRI) is continuously working to understand behavior of the rock mass through laboratory testing, field investigations and study on simulated models. Obtained experiences during these investigations are observed to be of strategic importance during application of a modern technology to improve practical mining conditions. This paper reviews rock mechanics aspects of different mechanized Pillar Extraction approaches during mining of a deep seated coal seam and, also attempts to present an appraisal of some of the recent technical developments to overcome the challenges of a deep underground coal mining.
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Impact of Stress Redistribution on Stability of workings during DePillaring
2006Co-Authors: Prabhat Kumar Mandal, Rajendra SinghAbstract:Extraction of underground coal during dePillaring operations in India Poses several ground control problems. Understanding the behaviour of Pillars and overlying roofs and sides in underground coal mines in important for design of efficient bord and Pillar Extraction system. Hence, knowledge of development of stresses, their magnitudes and redistributions with face advancement become critical. The analyses in this article have been undertaken for a mine to predict stress development and redistribution in and around Pillars and galleries during dePillaring which eventually assessed the ground stability to provide design guidelines for making ground control decisions in advance. Simulation of virgin state, developed panel and dePillaring operations with one-, two- and three- Pillars Extraction have been carried out. The simulation results reveal that the maximum principal stresses is developed on the immediate rib Pillar and there is 66% increase in the maximum stress level after three Pillar Extraction when compared to after one-Pillar Extraction when compared to after one-Pillar Extraction. The safety factor values of the rib Pillars, slice galleries, and immediate Pillars are decreased after three-Pillar Extraction. However, after one Pillar Extraction, it is found that the safety factor of the rib is more than one, thus it should be judiciously reduced for minimizing stress concentration inside the goaf. The simulation results also reveal that the thickness of the unstable zone in the immediate roof is 1.5 m where the safety factor is up to one. Above 1.5 m, the immediate roof is considered to be stable. The roof bolts used in the galleries are 1.5 m of length. It may be better, if a part of the roof bolts is grouted in the stable zone (that is, more that 1.5 m thickness) for effective working of the roof bolts. The simulation results are validated through continuous remote monitoring of the studied panel. The instrumentation-based observations strongly support the simulation results.
Hernanto Suparto - One of the best experts on this subject based on the ideXlab platform.
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ANALISA RANCANGAN PENGAMBILAN CADANGANPADA SILL PILAR (SILL Pillar Extraction) UNTUKSTOPE CIURUG L.500 LOKASI BLOK II SELATANUNIT BISNIS PERTAMBANGAN EMAS PONGKORPT. ANEKA TAMBANG Tbk.BOGOR JAWA BARAT
2013Co-Authors: Hernanto SupartoAbstract:PT. Antam, Tbk. Gold mining unit Pongkor (UBPE) located in Bogor Regency, West Java Province. In the power of the mining area there are three main vein being mined is Ciurug, Kubang Cicau, and Main Ciguha. To Ciurug level 500 myself using Cut and Fill mining, stope mining operations on multiple Ciurug have reached the limit in accordance with the end that has been recommended to the left sill Pillar at different thicknesses for each location. On the other hand, the left sill Pillar representing the remaining reserves, which could increase mine productivity, due to the current state of PT. Antam Tbk. - UBPE Pongkor trouble getting the front ore mining which can be eject safely. If there is an attempt at making up the rest of the sill Pillar should be done with a different approach but still consider the stability of the sill Pillar left. Approach to do that is by sill Pillar Extraction method is necessary for the analysis of the design concept.The evaluation is done by making modeling through Phase2 program that assisted with RocLab program for data preparation required material properties. Modeling is made in two stages, namely modeling existing conditions, and extract Pillar by means perslice with thick sill Pillar is 8 m. In this evaluation will be conducted each stope analysis can be based on the value of strength factor, displacement and safety factor that indicates the strength of the sill Pillar and stope is safe or not.Results demonstrate the value of existing stope on roof strength factor
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analisa rancangan pengambilan cadanganpada sill pilar sill Pillar Extraction untukstope ciurug l 500 lokasi blok ii selatanunit bisnis pertambangan emas pongkorpt aneka tambang tbk bogor jawa barat
2013Co-Authors: Hernanto SupartoAbstract:PT. Antam, Tbk. Gold mining unit Pongkor (UBPE) located in Bogor Regency, West Java Province. In the power of the mining area there are three main vein being mined is Ciurug, Kubang Cicau, and Main Ciguha. To Ciurug level 500 myself using Cut and Fill mining, stope mining operations on multiple Ciurug have reached the limit in accordance with the end that has been recommended to the left sill Pillar at different thicknesses for each location. On the other hand, the left sill Pillar representing the remaining reserves, which could increase mine productivity, due to the current state of PT. Antam Tbk. - UBPE Pongkor trouble getting the front ore mining which can be eject safely. If there is an attempt at making up the rest of the sill Pillar should be done with a different approach but still consider the stability of the sill Pillar left. Approach to do that is by sill Pillar Extraction method is necessary for the analysis of the design concept.The evaluation is done by making modeling through Phase2 program that assisted with RocLab program for data preparation required material properties. Modeling is made in two stages, namely modeling existing conditions, and extract Pillar by means perslice with thick sill Pillar is 8 m. In this evaluation will be conducted each stope analysis can be based on the value of strength factor, displacement and safety factor that indicates the strength of the sill Pillar and stope is safe or not.Results demonstrate the value of existing stope on roof strength factor <1.3, delta shows the roof displacement exceeding three elastic displacement (failure), and showing the roof safety factor ≤ 1.2 (failure), the left wall and the right wall ≥ 1.2 ( safe). 1 slice stope results demonstrate the value of strength factor on the left wall, roof, and walls tend to experience the same right which decrease when the time will be open stope, delta value of displacement on the left wall, roof, and walls have a right to point 4, point 4 and point 3 stated "failure", the value of the safety factor on the roof failure due to ≤ 1.2. Stope slice 2 shows the strength factor on the left wall and right up when stope will be opened, while the current decrease when the roof is opened, the value of delta displacement is smaller than three times the elastic displacement and factor of safety are only on the roof menunjakkan ≤ 1.2 (failure ). Stope slice 3 shows the strength factor values are left wall cavity so that the strength factor value = 0, the roof and walls fell right time to open. Delta displacement only just on the right wall there are three points that exceed three elastic displacement (failure). Security factor scores only on the roof showed ≤ 1.2 (failure) if when opened.
Rakesh Kumar - One of the best experts on this subject based on the ideXlab platform.
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Coal Pillar Extraction Under Weak Roof
Mining Metallurgy & Exploration, 2020Co-Authors: Arun Kumar Singh, Rajendra Singh, Rakesh Kumar, Ashok Kumar, Dheeraj Kumar, Sahendra Ram, Amit Kumar SinghAbstract:This article offers an examination of a retreat mining method conducted at the Pinoura Mine in India from 2010 to 2017. The method is atypical for coal mines of India’s coalfields. The method executes dePillaring in a single pass and does not require the formation of galleries and support installation in splits, thus, reducing the cycle time. A variety of observations are discussed throughout this work and emphasis is placed on field measurements and dePillaring under weak roof ( RMR = 40–45). This paper discusses design techniques, specifically the estimation of the snook (remnant Pillar) size, and important practical observations after the fact. The execution of this method was eventually conducted in eleven panels.
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Roof sagging limit in an early warning system for safe coal Pillar Extraction
International Journal of Rock Mechanics and Mining Sciences, 2019Co-Authors: Ashok Kumar, Rajendra Singh, Arun Singh, Rakesh Kumar, Dheeraj Kumar, Sahendra Ram, Abhishek Gautam, Amit Kumar SinghAbstract:Abstract Field studies have found that, generally, a roof fall takes place after certain amount of roof strata sagging. Recent applications of auto warning tell-tale (AWTT) instrument as an early warning system at different dePillaring panels found it to be simple, economical and efficient during the coal Pillar Extraction (called dePillaring). AWTT is able to watch the set value of roof sagging continuously in time. However, the application of AWTT experienced two practical issues: (i) fixing roof sagging warning value before the fall of overlying strata and (ii) deciding horizon above which its anchorage point of AWTT needs to be installed. Different field experiences noticed that an anchorage horizon at 10 m depth from the ceiling of a gallery works satisfactorily for goaf edge. But fixation of the roof sagging warning value, before the fall of overlying strata, is found to be complex. Generally, the warning value for a given site conditions is determined by extensive field monitoring and correlation of the roof sagging value at the goaf edge with corresponding roof falls. Field studies found that modulus of elasticity and thicknesses of immediate roof are important parameters in deciding the warning value of the roof sagging. These studies also indicated that the variation in size of the left-out ribs and goaf span influence the warning value. These observed facts about the warning value for an AWTT are studied in laboratory using a numerical modelling approach in FLAC3D. The results obtained through developed simulated models are found to be in close agreement with those of the field studies. Attempts are also made to quantify the influence of above-mentioned parameters over the warning value through collated results of different studied models. The obtained results of field and laboratory investigations are presented and discussed in this paper for strata control in a dePillaring panel.
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Coal Pillar Extraction at deep cover: With special reference to Indian coalfields
International Journal of Coal Geology, 2011Co-Authors: Rajendra Singh, Prabhat Kumar Mandal, Arun Singh, Rakesh Kumar, Amalendu SinhaAbstract:Majority of the developed Indian coal seams are lying under strong and massive overlying strata. Depth of cover of these coal seams, standing on Pillars, varies from 50 to 500 m. Present Pillar Extraction (dePillaring) practises of the country have, predominantly, adopted intermediate mechanisation along with few fully mechanised dePillaring faces. Most of these faces are operating at shallow cover. But the existing techno-economical conditions of the industry are attracting a fully mechanised dePillaring system for deep seated coal Pillars, which is likely to grow in near future. Here the circumstances of bord and Pillar mining are to face difficult surroundings, mainly, due to rock-mass characteristics and stress conditions of the deep horizon. Although these two parameters are difficult to be pre-assessed accurately, a couple of recent experiences of dePillaring at deep cover have shown their influence over efficiency and safety of the dePillaring. A review of Pillar Extraction practises of other coal producing countries, under varying geo-mining conditions, showed importance of these parameters for the dePillaring. Providing a brief review of underground coal Pillar Extraction scenario, this paper presents geo-technical challenges encountered during caving of massive roof strata at two deep Indian dePillaring faces. These two trials experienced problems of (a) roof instability (b) barrier Pillar instability and (c) Pillar-spalling/floor-heaving. In absence of an effective hard roof management approach these problems could simply be dealt, up to some extent, by improvement in competency of the natural support.
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An observational approach for assessment of dynamic loading during underground coal Pillar Extraction
International Journal of Rock Mechanics and Mining Sciences, 2011Co-Authors: Rajendra Singh, Prabhat Kumar Mandal, Aastha Singh, Jhareswar Maiti, Rashmi Singh, Rakesh KumarAbstract:On the basis of a large number of field investigations, in and around underground coal mining faces (bord and Pillar) in India, this paper discusses issues of measurement and analysis of strata control parameters. Requirement of different types of instruments along with their suitability to monitor the strata control parameters under varying geo-mining conditions of the existing coal mines is also briefly explained. On the basis of field experiences, it is observed that the type of instrument to be placed in and around a dePillaring face is more or less dependent upon the geo-mining conditions of the site. Field investigations showed that the continuous monitoring (in time) of these instruments, preferably with the help of a data-logger, can provide important information about performance of mining structures (bord and Pillar) during caving of a competent overlying roof stratum. However, in absence of a data-logger, a simple process: called as Combined-Instruments-Approach (CIA) is implemented for some improvement in visualization of overlying strata behavior through manually observed data of the instruments. Scope of application of this approach to anticipate caving behavior of strong and massive roof strata during conventional dePillaring practice is demonstrated through analysis of an actual field monitoring results.
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Rock Mechanics challenges of dePillaring at deep cover
2009Co-Authors: Arun Kumar Singh, Rajendra Singh, Prabhat Kumar Mandal, Rakesh Kumar, Amit Kumar Singh, Sahendra RamAbstract:Underground coal mining at deeper cover encounters difficult underground environment due to increase in gas content and rise in temperature transition of a mining practice from shallow to high depth cover encounters a big change in the rock mass characteristics and the stress condition becomes more complex. At higher depth of cover, the excavation starts encountering stress control regime rather than structural control behavior of the rock mass. Mechanisation and automation of underground mining activities is a solution to improve the performance of deeper mines but the approach should match with the rock mass and stress conditions of the site. Since inception, CIMFR (formerly, CMRI) is continuously working to understand behavior of the rock mass through laboratory testing, field investigations and study on simulated models. Obtained experiences during these investigations are observed to be of strategic importance during application of a modern technology to improve practical mining conditions. This paper reviews rock mechanics aspects of different mechanized Pillar Extraction approaches during mining of a deep seated coal seam and, also attempts to present an appraisal of some of the recent technical developments to overcome the challenges of a deep underground coal mining.