采动影响下断层活化失稳及能量释放规律研究

Study on law of fault activation,failure and energy release under influence of mining

为研究工作面开采邻近断层时断层活化致灾机理,基于理论分析与数值模拟的手段分析断层面应力场、位移场变化规律,探讨断层活化失稳面积变化趋势,并计算断层活化释放能量及传递到工作面的剩余能量。结果表明:断层活化分为初始活化、稳定活化、活化加剧、活化弱化4个阶段;断层活化位置由高位顶板处断层向煤层附近发展,底板处断层活化时间晚于顶板处断层。采动影响下断层面将出现剪切应力突降,导致能量释放;断层面剪切应力和剪切法向应力比值均呈现出稳定-增长-降低的趋势,但剪切法向应力比值变化滞后于剪切应力。采用断层活化失稳释放能量计算公式,计算工作面向断层方向推进过程中断层活化能量释放大小,计算结果与微震监测记录具有相似规律,佐证了计算方法的可行性。断层活化释放能量以负指数形式传递至工作面,断层初始活化、稳定活化、活化弱化阶段所释放的能量传递至工作面后剩余能量的量级小于10^(5)J,而活化加剧阶段释放能量传递至工作面后剩余能量大于10^(7)J。因此工作面与断层间距小于40 m时,受断层活化扰动影响较大,冲击危险性更高。

In order to study the mechanism of fault activation and disaster when the working face was mined near fault,the stress field and displacement field of the fault layer were analyzed,based on theoretical analysis and numerical simulation,the trend of fault activation and destabilization area was discussed.At the same time,the fault activation release energy and the residual energy transferred to the working face were calculated.The results show that the fault activation is divided into four stages:initial activation stage,stable activation stage,activation intensification stage,and activation weakening stage.The fault activation position develops from the fault at the high roof to the vicinity of the coal seam,and the activation time of the fault at the floor is later than that of the fault at the roof.Under the influence of mining,the shear stress of the fault surface drops abruptly and leads to energy release.The shear stress and the ratio(shear stress to normal stress)on the fault surface exhibits a trend of stability-growth-decrease,but the latter of them always lags behind the former.Using the calculation formula of the energy released by the activation and instability of the fault,the magnitude of the fault activation energy released as mining approaches the fault is calculated using the fault activation release energy formula.The calculation results are similar to the microseismic monitoring records,which proves the feasibility of the calculation method.The energy released by the activation of the fault is transferred to the working face in the form of a negative index.The energy released in the initial activation,stable activation,and activation weakening stages of the fault is transferred to the working face.During the activation intensification stage,the fault activation energy received by the working face is greater than 10^(7)J,and the fault activation energy received by the working face at other stages is less than 10^(5)J.Therefore,when the distance between the working face and the fault is less than 40 m,it is greatly affected by the disturbance of fault activation,and the impact risk is higher.