Large-Deformation Failure Mechanism of Coal-Feeder Chamber and Construction of Wall-Mounted Coal Bunker in Underground Coal Mine with Soft, Swelling Floor Rocks

In traditional vertical coal bunker systems, a coal-feeder chamber (CFC) must bear the whole weight of the bunker. However, maintenance of CFCs within soft, swelling floor rock is a challenge faced in underground coal mines. Floor-heave control is a complex problem and is still not well-solved. Moreover, there is no report on the construction of bunker without a CFC, especially under such weak floor-rock conditions. Based on the serious CFC collapse case at Xiashijie mine, China, this work analyzed the deformation characteristics, main influencing factors, and failure mechanisms of the CFC using a FLAC numerical model. The results indicate that the intrusion of water weakens the strength of the floor rock and causes significant expansive forces; thus, large deformations and tensile failure occur first in the floor, further causing shearing and tensile damage of the reinforced column and even overall instability of the CFC. Then, a new wall-mounted coal bunker (WMCB), without building the CFC, is proposed. The FLAC3D program was adopted to study the stability of the rocks surrounding the new bunker, and an optimized reinforcement scheme was determined. More importantly, a self-bearing system, which includes self-designed H-steel beams, H-steel brackets, and self-locking anchor cables, was proposed and constructed to bear the whole weight of the bunker. The stability of WMCB was verified by a theoretical safety assessment and field test. The invented WMCB could remain stable in spite of severe floor heave. This work can provide helpful references for the construction of vertical bunkers without CFCs in coal mines with soft, swelling floor rocks.

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