动静载作用下逆冲断层力学失稳机制研究

Mechanical instability mechanism of thrust fault under static and dynamic loading

冲击地压往往发生在逆冲断层等地质构造附近,并且煤矿井下集中静载荷、顶板断裂等动载荷均对逆冲断层失稳具有重要的影响。基于典型逆冲断层工程实例的冲击显现特征分析,研究了静载荷作用下逆冲断层的活化过程以及采动应力场、位移场动态演化规律,通过施加动载应力波分析了逆冲断层的动力学响应特征,结合动静载作用下逆冲断层的力学特点,建立了断层失稳的多滑块-弹簧力学模型,并提出了逆冲断层冲击地压防治技术。研究结果表明:开采引起覆岩裂隙扩展并与断层带贯通是断层活化的直接原因;开采活动对断层的扰动呈现明显的分区性,扰动顺序是先上部、再中部、最后下部,且应力要先于位移受影响;动载对断层的扰动也是分区域的,将导致上部先失稳;采动并不是直接导致整个断层的滑移,而是优先引起某个或连续几个子系统的"局部失稳";基于动静载失稳理论的逆冲断层冲击地压防治技术主要包括深孔断顶爆破、煤层卸压技术、断底爆破等。

The coal bump often occurs near the geological structures such as thrust fault, and the concentrated static load and the dynamic load of roof fracture under the coal mine all have important effect on the stability of thrust fault. Based on analyzing the features of typical thrust-fault coal bump, process of fault activation and the dynamic evolution law of stress field and displacement field of thrust fault under static load have been studied, and dynamic response characteristics of thrust fault has been analyzed by applying dynamic stress wave. A "multi-sliding block-spring" mechanical model of fault insta bility is proposed based on the mechanical characteristics of thrust fault under dynamic and static load and prevention technology of thrust fault coal bump has also been put forward. The results of the study have shown that cracks of overlying strata caused by mining extension and connection with fault zone, which is the direct reason of fault activation;the perturbation of fault by mining activity is obviously partitional, namely, the perturbation sequence is first the upper, then the middle and finally the lower, and in the sensitivity to mining activity, stress is affected before displacement. The disturbance of dynamic load to fault is also regional, which will lead to instability of the upper. The slip of fault caused by mining is the "local instability" in one or several subsystems, and not the whole one. Prevention technologies of coal bump mainly contain deep hole blasting of hard roof, pressure relief of coal seam and blasting of hard floor.