Preprint Article Version 1 This version is not peer-reviewed

A Case Study on Large Deformation Failure Mechanism of Coal given Chamber and Invention of a New Wall-Mounted Coal Bunker in Xiashijie Coal Mine with Soft, Swelling Floor Rock

Version 1 : Received: 20 October 2017 / Approved: 20 October 2017 / Online: 20 October 2017 (15:31:57 CEST)

How to cite: Wang, X.; Xie, W.; Jing, S.; Bai, J.; Su, Z. A Case Study on Large Deformation Failure Mechanism of Coal given Chamber and Invention of a New Wall-Mounted Coal Bunker in Xiashijie Coal Mine with Soft, Swelling Floor Rock. Preprints 2017, 2017100141 (doi: 10.20944/preprints201710.0141.v1). Wang, X.; Xie, W.; Jing, S.; Bai, J.; Su, Z. A Case Study on Large Deformation Failure Mechanism of Coal given Chamber and Invention of a New Wall-Mounted Coal Bunker in Xiashijie Coal Mine with Soft, Swelling Floor Rock. Preprints 2017, 2017100141 (doi: 10.20944/preprints201710.0141.v1).

Abstract

Serious damage caused by floor heave in the coal given chamber of a vertical coal bunker is one of the challenges faced in underground coal mines. Engineering practice shows that it is more difficult to maintain the coal given chamber (CGC) than a roadway. More importantly, repairing the CGC during mining practice will pose major safety risks and reduce production. Based on the case of the serious collapse that occurred in the bearing structure of the CGC at the lower part of the 214# coal bunker in Xiashijie mine, China, this work analysed (i) the main factors influencing floor heave and (ii) the failure mechanism of the load-bearing structure in the CGC using FLAC2D numerical models and expansion experiment. The analysis results indicate that: the floor heave, caused mainly by mine water, is the basic reason leading to the instability and repeated failure of the CGC in the 214# coal bunker. Then a new coal bunker, without building the CGC, is proposed and put into practice to replace the 214# coal bunker. The FLAC3D software program is adopted to establish the numerical model of the wall-mounted coal bunker (WMCB), and the stability of the rock surrounding the WMCB is simulated and analysed. The results show that: (1) the rock surrounding the sandstone segment is basically stable. (2) The surrounding rock in the coal seam segment, which moves into the inside of the bunker, is the main zone of deformation for the entire rock mass surrounding the bunker. Then the surrounding rock is controlled effectively by means of high-strength bolt–cable combined supporting technology. According to the geological conditions of the WMCB, the self-bearing system, which includes (i) H-steel beams, (ii) H-steel brackets, and (iii) self-locking anchor cables, is established and serves as a substitute for the CGC to transfer the whole weight of the bunker to stable surrounding rock. The stability of the new coal bunker has been verified by field testing, and the coal mine has gained economic benefit to a value of 158.026174 million RMB over three years. The new WMCB thus made production more effective and can provide helpful references for construction of vertical bunkers under similar geological conditions.

Subject Areas

Vertical coal bunker; Coal given chamber; Floor heave; Wall-mounted coal bunker; Reinforcement; Self-bearing system

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