采动影响下断层渐进破坏过程及能量释放规律研究

Progressive failure process and energy release law of fault induced by coal exteaction

为研究工作面开采遇断层时断层渐进破坏过程及能量释放规律,基于数值模拟手段,分析逆断层下盘开采时断层周围应力环境变化特征及断层活化能量释放规律,并开展双轴加卸载试验,分析不同应力状态下断层单元试件破坏过程、剪应力变化规律及能量释放大小。结果表明:采动影响下,距煤层较远的高位顶板处断层水平应力降低,距煤层较近的顶底板处断层垂直应力增大,导致侧压系数减小,诱发断层活化失稳;断层破坏时发生黏滑失稳,出现多次剪应力突降,并伴随有能量的释放,其中第1次剪应力突降数值最大,且随着加卸载速率增大,剪应力突降数值增大;工作面向断层方向推进过程中,高位顶板处断层最先活化失稳释放能量,剪应力降及能量释放相对较小,煤层附近顶底板处断层活化失稳时间较晚,但剪应力降及能量释放数值较大,易造成大的矿震甚至诱发冲击事故。

In order to study the progressive failure process and energy release law of fault when the mining encounters a fault,the experiment and numerical simulation research were carried out.Based on the numerical simulation,the characteristics of the stress environment around the fault and the law were analyzed of the activation energy release of the fault during reverse fault footwall mining.Biaxial loading and unloading tests were carried out to analyze the damage process,shear stress variation and energy release of fault element specimens under different stress states.The results show that,under the influence of mining,the horizontal stress of the fault decreases at the high roof far from the coal seam,while the vertical stress of the fault increases at the roof and floor nearer to the coal seam,which leads to the decrease of lateral pressure coefficient and induces the activation instability of the fault.Stick-slip instability occurs during the fault activation,which induces multiple sudden drops in shear stress and leads to energy release.When the shear stress drops suddenly for the first time,the value of the drop is the largest.The shear stress sudden drop value increases with the augment of loading and unloading rate.During the mining activities approach the fault,the fault at the high roof activates first and release energy,and the shear stress drop and energy release are relatively small.The activation and destabilization time of the fault at the roof and floor near the coal seam is relatively late,but the shear stress drop and energy release value is larger.When mining is gradually approaching the fault,it is easy to cause large mine earthquake or even induce impact accidents.