Numerical modelling of out-of-seam dilution in longwall retreat mining |
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| Authors: | G Saeedi K Shahriar B Rezai C Karpuz |
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| Affiliation: | 1. Department of Mining and Metallurgical Engineering, Amirkabir University of Technology, Iran;2. Department of Mining Engineering, Middle East Technical University, Turkey;1. Flight Technology College, Civil Aviation University of China, Tianjin, 300300, China;2. Key Laboratory of Gas and Fire Control for Coal Mines (China University of Mining and Technology), Ministry of Education, Xuzhou, 221116, China;3. Faculty of Safety Engineering, China University of Mining and Technology, Xuzhou, 221116, China;4. National Engineering Research Center for Coal and Gas Control, China University of Mining and Technology, Xuzhou, 221116, China;5. Faculty of Resources and Safety Engineering, China University of Mining and Technology (Beijing), Beijing, 100083, China;1. School of Mines, China University of Mining & Technology, Xuzhou 221116, China;2. State Key Laboratory of Coal Resource and Mine Safety, China University of Mining & Technology, Xuzhou 221116, China;3. Coal and Electricity of Anhui Hengyuan Co. Ltd., Huaibei 235162, China;1. Engineering Geology and Resource Geotechnics Group, Simon Fraser University, Burnaby, BC, Canada;3. Coal Mining and Designing Department, Tiandi Science and Technology Co. Ltd., Beijing, China;1. State Key Laboratory of Coal Resource and Safe Mining, Xuzhou 22116, PR China;2. School of Mines, China University of Mining and Technology, Xuzhou 221116, PR China;3. Yuwu Coal Industry Corporation Ltd., Changzhi 046103, PR China;1. School of Civil and Resource Engineering, University of Science and Technology Beijing, Beijing 100083, China;2. State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, Xuzhou 221116, China;3. Zhong-an Academy of Safety Engineering, Beijing 100083, China |
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| Abstract: | Longwall mining is a common mining method in Iran that is often affected by out-of-seam dilution (OSD). The field investigations performed in Tabas coal mine show that OSD often occurs due to roof falls in front of the face area before support setting and also removing some floor material. The increase in unsupported roof span above the shearer may cause difficulty in controlling the roof and consequently increases dilution of the run of mine (ROM) coal. The paper presents the results of a study on some dominant factors causing OSD in prop-free front of the face in longwall retreat mining method. A series of two-dimensional numerical models are developed and analyzed to examine the effects of mining depth, in-situ stress, unsupported roof geometry above the shearer as well as roof and floor strata quality and dip of coal seam on OSD. Two criteria were established, one considers the roof falls, defined as low stress level or plasticity zones under yield tension which roof material unravels and other is about removing floor, defined as depth of support and shearer sinking into the floor. The equivalent linear relaxation depth (ELRD) and depth of removing floor (DRF) concepts were used to quantify OSD. The methodology presented in this study is useful since it can be applied to develop mine-specific design tools for the prediction of OSD. |
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