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| Experimental study of floor cracking under deep mining |
| CHEN Juntao1，2，3，GUO Weijia1，YIN Liming1，LU Chang1，CHANG Xikun1，ZHANG Shichuan1，ZHANG Chengxiang4 |
| (1. State Key Laboratory of Mining Disaster Prevention and Control Co-founded by Shandong Province and the Ministry of Science and Technology，Shandong University of Science and Technology，Qingdao，Shandong 266590，China；2. Henan Key Laboratory for Green and Efficient Mining and Comprehensive Utilization of Mineral Resources，Henan Polytechnic University，Jiaozuo，Henan 454000，China；3. College of Geosciences and Surveying Engineering，China University of Mining and Technology(Beijing)，Beijing 100083，China；4. Shandong Energy Zibo Mining Group Co.，Ltd.，Zibo，Shandong 255100，China) |
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Abstract In order to study the failure mechanism of deep floor rock，a model of mining cracking and conduit formation in floor rock with small faults was established based on the test system developed in-house with high water pressure to simulate the floor water inrush. The stress and displacement sensors were set up at different depths of the floor，and the stress and displacement of the floor and the fault rock around the mining face were studied. The crack development and propagation in the floor and fault rock was derived with the inverse simulation. Two trends of the stress in the floor rock during mining at the working face occurred. In the first case，the stress increment in the floor rock under the pillar on the left open-off cut increased at first and then decreased. In the second case，the stress increment in the floor rock under the stope increased at first，then decreased to zero and finally increased at the opposite direction. The deep mining cracks mainly appeared in the corresponding floor of open-off cut，goaf and mining working face dominated by the vertical tensile cracks，shear cracks and layer cracks. Some small cracks were generated from the tips of the main crack. The larger stress differences were formed in the hanging wall and the footwall rock of fault close to the coal seam. A strip of long shear crack parallel to the fault strike was presented in the fault hanging wall due to the large shear stress difference，which promoted the sliding and the fault activation.
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2016, Vol. 35 
