scholarly journals Optimization of roadway layout in ultra-close coal seams: A case study

PLoS ONE ◽  
2018 ◽  
Vol 13 (11) ◽  
pp. e0207447 ◽  
Author(s):  
Gang Wu ◽  
Xinqiu Fang ◽  
Hualin Bai ◽  
Minfu Liang ◽  
Xiukun Hu
Keyword(s):  
Coal Seams ◽  
Close Coal Seams

scholarly journals Comprehensive technical support for safe mining in ultra-close coal seams: A case study

2021 ◽  
pp. 014459872110093
Author(s):  
Wei Zhang ◽  
Jiawei Guo ◽  
Kaidi Xie ◽  
Jinming Wang ◽  
Liang Chen ◽  
...  
Keyword(s):  
Coal Seam ◽  
Technical Support ◽  
Surrounding Rock ◽  
Coal Seams ◽  
Deformation Control ◽  
Hard Roof ◽  
Working Face ◽  
Close Coal Seams ◽  
Safe Mining

In order to mine the coal seam under super-thick hard roof, improve the utilization rate of resources and prolong the remaining service life of the mine, a case study of the Gaozhuang Coal Mine in the Zaozhuang Mining Area has been performed in this paper. Based on the specific mining geological conditions of ultra-close coal seams (#3up and #3low coal seams), their joint systematic analysis has been performed, with the focus made in the following three aspects: (i) prevention of rock burst under super-thick hard roof, (ii) deformation control of surrounding rock of roadways in the lower coal seam, and (iii) fire prevention in the goaf of working face. Given the strong bursting tendency observed in upper coal seam and lower coal seam, the technology of preventing rock burst under super-thick hard roof was proposed, which involved setting of narrow section coal pillars to protect roadways and interleaving layout of working faces. The specific supporting scheme of surrounding rock of roadways in the #3low1101 working face was determined, and the grouting reinforcement method of local fractured zones through Marithan was further proposed, to ensure the deformation control of surrounding rock of roadways in lower coal seams. The proposed fire prevention technology envisaged goaf grouting and spraying to plug leaks, which reduced the hazard of spontaneous combustion of residual coals in mined ultra-close coal seams. The technical and economic improvements with a direct economic benefit of 5.55 million yuan were achieved by the application of the proposed comprehensive technical support. The research results obtained provide a theoretical guidance and technical support of safe mining strategies of close coal seams in other mining areas.

scholarly journals Cooperative Control Mechanism of Long Flexible Bolts and Blasting Pressure Relief in Hard Roof Roadways of Extra-Thick Coal Seams: A Case Study

2021 ◽  
Vol 11 (9) ◽  
pp. 4125
Author(s):  
Zhe Xiang ◽  
Nong Zhang ◽  
Zhengzheng Xie ◽  
Feng Guo ◽  
Chenghao Zhang
Keyword(s):  
Coal Seam ◽  
Cooperative Control ◽  
Field Tests ◽  
Surrounding Rock ◽  
Deep Hole ◽  
Coal Seams ◽  
Thick Coal Seam ◽  
Structure Damage ◽  
Hard Roof

The higher strength of a hard roof leads to higher coal pressure during coal mining, especially under extra-thick coal seam conditions. This study addresses the hard roof control problem for extra-thick coal seams using the air return roadway 4106 (AR 4106) of the Wenjiapo Coal Mine as a case study. A new surrounding rock control strategy is proposed, which mainly includes 44 m deep-hole pre-splitting blasting for stress releasing and flexible 4-m-long bolt for roof supporting. Based on the new support scheme, field tests were performed. The results show that roadway support failure in traditional scenarios is caused by insufficient bolt length and extensive rotary subsidence of the long cantilever beam of the hard roof. In the new proposed scheme, flexible 4-m-long bolts are shown to effectively restrain the initial expansion deformation of the top coal. The deflection of the rock beam anchored by the roof foundation are improved. Deep-hole pre-splitting blasting effectively reduces the cantilever distance of the “block B” of the voussoir beam structure. The stress environment of the roadway surrounding rock is optimized and anchorage structure damage is inhibited. The results provide insights regarding the safe control of roadway roofs under extra-thick coal seam conditions.

scholarly journals Roof Movement and Failure Behavior When Mining Extra-Thick Coal Seams Using Upward Slicing Longwall-Roadway Cemented Backfill Technology

2020 ◽  
Vol 2020 ◽  
pp. 1-15 ◽  
Author(s):  
Xuejie Deng ◽  
Zongxuan Yuan ◽  
Lixin Lan ◽  
Benjamin de Wit ◽  
Junwen Zhang
Keyword(s):  
Mechanical Analysis ◽  
Movement Behavior ◽  
Failure Behavior ◽  
Mining Method ◽  
Coal Seams ◽  
Flat Bottom ◽  
Final State ◽  
Performance Requirements ◽  
Cemented Backfill

A novel and environmental-friendly backfill mining method known as upward slicing longwall-roadway cemented backfill (USLCB) technology has recently been proposed and successfully applied in mines extracting extra-thick coal seams located under sensitive areas. This paper studies the effects USLCB had on roof movement and failure behavior using the mechanical analysis approach. The application of USLCB in the Gonggeyingzi Mine is taken as a case study with roof movement behavior being monitored over a single mining cycle, as well as over multiple mining cycles of different coal slices. In addition, backfill performance requirements to prevent roof failures where USLCB is implemented are studied. The results show that the deflection curves of the roof at the end of each mining cycle during mining the first and the six slices are symmetrical, but they change from asymmetrical to symmetrical during the mining progresses of the second slice to the fifth slice. The final state of roof movement after the first slice, and through to the fifth slice, displays an obvious “flat bottom” pattern in the middle of the deflection curve. The roof movement during the removal of the top slice is noticeably different from other slices. The results also show that the requirements of the elastic modulus, as well as the strength of the backfill, increase as the number of mined slices increases from 1 to 5, but the requirements drop sharply for mining the top slice.

scholarly journals Stability of Split-Level Gob-Side Entry in Ultra-Thick Coal Seams: A Case Study at Xiegou Mine

Energies ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 628 ◽  
Author(s):  
Junwen Zhang
Keyword(s):  
Coal Mine ◽  
Coal Pillar ◽  
Peak Stress ◽  
Coal Seams ◽  
Solid Coal ◽  
Stress Fluctuation ◽  
Pillar Mining ◽  
The Stability ◽  
Rock Specimens

Split-level longwall gob-side entry (SLGE) has been applied as a special form of small gate pillar mining (or non-coal pillar mining) in thick coal seams. The stability of the coal pillar directly affects the rationality of the layout of the SLGE. Starting from the mining-induced influence around the SLGE, this paper compares the mechanical properties of coal under different mining effects, and studies the rationality of “zero pillar” location against the Xiegou coal mine. The study shows that the key to success of the application of the SLGE is the existence of an intact zone within the triangular coal pillar in spite of double disturbances due to tunneling and coal mining extraction. Laboratory testing shows that the density and uniaxial compressive strength of rock specimens obtained from the triangular coal pillar are smaller than that from the other part of the panel which is concluded to be due to the varied degree of mining-induced influence. The numerical modeling results show that most of the triangular coal pillar is intact after extraction of the panel, and that the peak stress is located in the solid coal beyond the triangular coal pillar. The plastic zone of the triangular coal pillar is only about 1 m after the excavation of the tail gate of the next split-level panel. The physical modeling shows that the tail gate of the next panel is in the destressed zone with only a very small stress fluctuation during the extraction of the next panel. The study shows that the location of the SLGE at Xiegou coal mine is reasonable. SLGE is preferable for ultra-thick coal seams.

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