Normal Fault Activation Laws And Mining Stress Evolution Characteristics Of Working Face Mining

Faults are the most common causes and have larger influenced geological structure in Chinese coalmines. Due to the discontinuity of the rocks cut by the fault, the distribution of the mining stress is abnormal and the mining effect shows notable which would easily induced the dynamic disasters and has a great influence on design and safe production of the coalmine.The evolutionary laws of the roof subsidence of the two fault walls,mining stress and the fault activation affected by the mining operations with the working face on footwall or hanging wall passing through a normal fault can be studied utilizing theoretical calculation, physical simulation and the numerical simulation, he results of the numerical simulation are verified via the engineering case of the microseismic events. The results can be verified via the engineering case of the microseismic events. Hence, the main findings of the study are shown as fallows:1) When the working face in the footwall or the hanging wall advances toward the normal fault, the peak value of the front abutment stress rises gradually with the decreasing of the fault coal-pillar; and then the peak value would reduces due to the plastic failure of the coal pillar with the strength exceeding the ultimate strength. When the hanging wall mining, the stable structure of the main roof is easier formed than that of the footwall and the block effect of the fault is not obvious relatively due to the good capability of the loading transmission from the hanging wall,while the block effect of the fault is notable and the sudden increase of the abutment stress occurs when the footwall mining.2) The stress variation of the fault plane has the notable spatiotemporal characteristics. The stress of the high-located fault plane would change firstly affected by the mining operations easily; the sensitivity of the shear stress and the normal stress is different at same point of the fault plane, of which the normal stress is first to be affected,and then the shear stress changes.3) From the numerical simulation and the physical simulation, it can be concluded that when the working face in the footwall passes through the fault, the possibility of the fault activation is highest in the range of the -30?30m which results from the violent movement of the overlying strata of the two fault walls; therein, the footwall strata is easily global slip along the fault plane while the main roof of the hanging wall is more easily cutting globally during the range of -20?-30m. When the working face in the hanging wall passes through the fault, the possibility of the fault activation is highest in the range of the -20?0m and the violent movement of the overlying strata with -70?0m; The breaking line of the overlying strata develops to the fault obliquely and links up with the fault plane, the rock burst is easily induced due to the break of the footwall strata.4) Along with the advance of the fault, the high fault is affected by mining at first, and then extends to the ends of the fault in the vertical direction. Compared with the fault surface of the upper wall, the sudden increase of the abutment stress occurs when the footwall mining, fault activation start time is earlier and the two plate movement is more severe,so the risk is bigger.5) The mining stress and fault activation are affected notably by the dip angle of the fault and mining thickness of the coal seam, while the fall height is not obvious.