Realization method and influencing factors of excavation⁃induced slip for locked fault

The project ‘experiment system for modeling fault⁃slip burst in underground coal roadways’ supported by National Major Scientific Research Equipment aims to develop a large⁃scale 3D physical modelling instrument for fault⁃ slip burst. The realization of fault slip is the primary problem faced by the project. To obtain the realization method of excavation⁃induced fault slip，the fault structures including locked sections were proposed，and the tests of excavation⁃ induced slip for single fault and double faults layouts were designed. Through physical and numerical simulation tests，the effects of loading plate friction，fault dip and confining pressure on fault slip and fracture of the locked section were systematically studied，and preliminary suggestions for instrument design were given. The results show that 1 the ‘three directions and four sides’ loading method is suitable for the physical modelling instrument for fault⁃slip burst. A single⁃fault layout or a double⁃fault layout can be adopted for the model body and a rock bridge type locked section is recommended for the fault structure. 2 Under three⁃dimensional loading conditions，fault slip can be successfully induced by the instantaneous excavation at the bottom of the fault hanging wall. After excavation，the mod⁃ el body above the excavation is locally damaged，and the boundary stress in the main slip direction of the fault is re⁃ duced. The recovery of the boundary stress in the main slip direction of the fault applies loads on the residual hanging wall of the fault，which causes the fault to slip at the locked section and shear fracture in the locked section. 3 The fault slip behavior is affected by the friction of the loading plate，the fault dip and the confining pressure. The fric⁃ tion coefficient of the loading plate should not exceed 0.2. For a single⁃fault layout，the fault dip angle should not be less than 50°，and for a double⁃fault layout，the dip angle of the fault to be slipped should not be less than 60°. The boundary stress in the main slip direction of the fault should be much larger than the boundary stress in the fault tend⁃ ency direction，and the boundary stress in the fault strike direction should be greater than the boundary stress in the fault tendency direction.