开挖诱导锁固断层滑移的实现方式及影响因素
Realization method and influencing factors of excavation⁃induced slip for locked fault
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摘要: 国家重大科研仪器研制项目“ 煤矿巷道断层滑移型冲击地压模拟试验系统” 旨在研制大型 三维断层滑移型冲击地压物理模拟仪器,断层滑移的诱导实现是项目面临的首要难题。 为获得开 挖诱导断层滑移的合理实现方式,提出了包含锁固段的断层结构形式,设计了单断层和双断层布置 条件下开挖诱导断层滑移的试验方案,开展了相似模拟试验和数值模拟试验,系统研究了加载板摩 擦、断层倾角和围压对断层滑移和锁固段破断的影响,给出了仪器设计的初步建议。 研究结果表 明:1 断层滑移型冲击地压物理模拟仪器适合采用“三向四面”加载方式,模型体可采用单断层布 置或双断层布置,断层结构可采用岩桥型锁固段。 2 在三维加载条件下,断层上盘底部瞬时开挖 可成功诱导断层滑移。 开挖后开挖空间上方模型体发生局部破坏,断层主滑方向边界应力降低;断 层主滑方向边界应力恢复对残留断层上盘形成加载,导致断层在锁固段处滑移、锁固段被剪断。3 断层滑移行为受加载板摩擦、断层倾角与围压的共同影响。 加载板摩擦因数应不超过 0.2;单断 层布置时,断层倾角应不小于 50°,双断层布置时(边界断层倾角为 45°),滑移断层倾角应不小于60°;断层主滑方向边界应力应远大于断层倾向方向边界应力,断层走向方向边界应力应大于断层 倾向方向边界应力。Abstract: 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.