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Minerals 2017, 7(6), 96; doi:10.3390/min7060096

Mechanism of Surrounding Rock Failure and Crack Evolution Rules in Branched Pillar Recovery

1
Center of Rock Instability and Seismicity Research, School of Resources and Civil Engineering, Northeastern University, Shenyang 110819, China
2
Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines, Northeastern University, Shenyang 110819, China
3
Institute of Mining Engineering, Beijing General Research Institute of Mining & Metallurgy, Beijing 100160, China
*
Author to whom correspondence should be addressed.
Academic Editor: Abbas Taheri
Received: 11 March 2017 / Revised: 29 May 2017 / Accepted: 2 June 2017 / Published: 8 June 2017
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Abstract

To study the mechanism of surface collapse and crack evolution in a roadway chain failure process in the pillar recovery of Hongling lead zinc ore in Inner Mongolia Province, China, microseismic monitoring technology, moment tensor theory, and numerical simulation are used for the inversion of rock mass fracturing, the destruction type classification of crack, and the mechanism of surrounding rock. Research shows the following: (1) the rock mass fracturing is first produced within the +955 m level, before extending through the hanging wall to the ground surface. Then, many shear failures occur in the ground surface of the footwall, extending downwards in an arc-shaped path to the +905 m level. Finally, the surface gradually collapses with large-scale shear failures. (2) The mechanism of surface collapse is as follows: after the recovery of pillars in the +905 m level, tensile cracks generated in the top of orebody #2 extend upwards and obliquely. Analogously, shear cracks are generated in the top of orebody #1, extending upwards. After the recovery of pillars in the +855 m level, the marble interlayer is destroyed and sinks, and many tensile cracks and shear cracks exist and incise in the ground surface, which cause the ground surface to collapse. (3) The mechanism of crack evolution is as follows: after the recovery of 5107 pillars, the footwall haul road in the +905 m level was damaged and collapsed by the cut-through cracks. Those cracks then continue to extend upwards and converge with the slanting shear cracks in the +905 m level, which form a triangular failure in the footwall rock. Finally, the failure causes the tensile and shearing cracks in the haulage way of the +955 m level to extend and connect, which forms the haulage way chain failure. View Full-Text
Keywords: moment tensor theory; microseismic monitoring; numerical simulation; surface collapse; failure mechanism; crack evolution rule moment tensor theory; microseismic monitoring; numerical simulation; surface collapse; failure mechanism; crack evolution rule
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Hu, G.; Yang, T.; Zhou, J.; Yu, Q.; Xie, L.; Liu, H.; Zhao, Y. Mechanism of Surrounding Rock Failure and Crack Evolution Rules in Branched Pillar Recovery. Minerals 2017, 7, 96.

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