基于应力波理论的断层对覆岩移动变形和应力传递阻隔效应研究

为了研究断层对开采沉陷影响机制,将工作面开采对覆岩的扰动视为应力波在岩层介质中的传递,建立了应力波在软弱岩层和坚硬岩层间双向传递的应力表达式。采用理论和数值计算分析了软弱岩层介质对应力波传递的影响,揭示了断层对覆岩移动变形和应力传递阻隔机制并通过相似模拟进行验证,最后利用数值计算分析了不同断层特征参数对覆岩移动变形阻隔作用的影响程度。结果表明：工作面开采产生的应力波波速越大,采动对覆岩的扰动越大|断层带岩体作为破碎带存在,应力波在断层带岩体多重反射作用下穿过断层带后波速下降明显,开采盘与非开采盘应力波最大波速之比为4.68～35.61,断层对采动应力传递具有阻隔效应,覆岩移动变形主要发生在开采盘|由于应力波穿越断层后在浅部波速衰减小于深部,浅部断层带岩体先于深部断层带岩体发生非连续变形|断层特征参数对覆岩移动变形传递阻隔作用排序为断层带宽度＞断层落差＞断层倾角＞断层带岩体内摩擦角＞断层带岩体黏聚力。

Study on fault barrier effect on overburden deformation and stress transfer based on stress wave theory

Surface subsidence laws under the influence of fault is significantly different from that under common geological conditions. In order to study mining subsidence mechanism influenced by fault, the disturbance of working face mining on overlying rock is regarded as the transfer of stress wave in rock stratum medium. At the same time, the stress expressions of wave transferring from weak rock to hard as well as from hard rock stratum to weak are established. Stress wave transmission influenced by weak strata medium is ana-lyzed by theory and numerical calculation to reveal the mechanism of fault barrier to overburden movement and stress transfer. At last, it’s verified by similar model experiment and the influence of different fault characteristic parameters on the barrier is analyzed by numerical calculation. The study has showed that firstly, the disturbance of mining on overlying rock is closely related to the stress wave velocity generated by mining, and the greater the stress wave velocity is, the greater the disturbance of mining on overlying rock is. Secondly, fault rock mass being as fractured zone, stress wave velocity decreased significantly after through the fault zone under the action of multiple reflection effect. The ratio of maximum stress wave velocity according to mining wall and the other side is 4.68 ~ 35.61. Fault has an obvious blocking effect on the transfer of mining-induced stress wave, that is, the fault has a blocking effect on the transfer of min-ing-induced stress, and the overburden movement and deformation mainly occur in the mining wall. Lastly, for the reason that the stress wave velocity attenuation in shallow fault zone is less than that in deep fault zone, the rock mass in shallow fault zone has discontinuous deformation before the rock mass in deep fault zone. The order of transmission and barrier effect of fault characteristic parameters on overburden movement and deformation is fault zone width > fault drop > fault dip Angle > friction angle > cohesion. The results are of practical significance to the analysis of surface subsidence laws influenced by fault and the protection of surface structures at outcrops.