煤矿开采活动对断层系统的卸荷效应，往往诱发逆冲断层失稳进而导致冲击地压灾害。以义马F16逆冲断层为工程背景，采用实验室实验研究了卸载条件下逆冲断层的差应力变化特征，分析了逆冲断层卸载过程中的位移场、变形场演化规律，阐述了逆冲断层失稳瞬态的滑移位移及声发射特性，探讨了逆冲断层的失稳过程。研究结果表明：逆冲断层卸载失稳时发生多次差应力“突跳”现象，以首次“突跳”变化量最大，差应力突变量为0.36 MPa；断层不同部位滑移情况具有显著差异，其中下部滑移量大于中部和上部、下盘远场滑移量大于近场和上盘；断层岩体的法向应变和剪切应变呈“降低—突增—波动—稳定”的变化趋势，且变形场受位置影响较大，如下部法向应变“突跳”量大于中部和下部，两端剪切应变“突跳”量大于中部；断层失稳瞬间可分为启滑、主震、后震3个阶段，主震将释放大部分能量，为断层冲击地压的主要能量来源；卸载导致逆冲断层滑移的过程分为线性稳态、非线性稳态、亚失稳及失稳4个阶段，失稳瞬间剪应变的变化趋势为“突降—回弹—稳定”；开采扰动引起的卸荷作用，造成F16断层不同位置呈不同的滑移模式，即浅部逆时针滑移、深部顺时针错动。

The unloading effect induced by coal mining often leads tothe rupture of thrust fault and then causes rock burst.Takingthe F16 thrust fault of Yimamining area as an example, the experiment of thrust fault slipping was conducted under unloading.Based on the experiment result, the differential stress variation, the evolution of displacement and strain field along the fault were studied.Furthermore, the transient slip displacement and acoustic emission characteristics were analyzed and the process of thrust fault slipping was discussed. The results show that① the differential stress jumps repeatedly when the fault slips, among which the first “jump”, 0.36MPa, is the biggest one. ②Different points along the fault have different slippages. The slippage of the lower part is larger than that in the middle and upper part, so asthe slippage in the far field of footwall is larger than that in the near field and the upper wall.③The normal strain and shear strain monitored by the strain gauges arranged along the fault line change as "decline-surge-fluctuate-stable" during the fault slipping. Also, the strain field differentiates as the fault's monitoring points change. The differentiation is that the normal strain's rupture at the lower part of the fault is larger than that at the middle and lower part, while the shear strain's rupture at both ends of the fault is larger than that at the middle.④When the fault ruptures, three phrasesincluding sliding initiation, main earthquake and aftershock occur, along with the main earthquake releasing most energy, which is the energy source of fault rock-burst. The whole course of thrust fault unloading contains four phrases, linearly increasing, nonlinearly increasing, meta-stable and rupture. When the fault ruptures, shear strain first suddenly drops, then rebounds and becomes stable at last. In practice, the unloading effect causes different patterns of the F16 fault slipping, namely the upper part of the F16 fault slips anticlockwise and the deeper part ruptures clockwise.

1 实验背景

3 实验方案

   3.1 试样

   3.2 加卸载方案

   3.3 监测方案

4 实验结果

   4.1 单侧卸载逆冲断层失稳的差应力“突跳”

   4.2 逆冲断层卸载失稳的位移场时空演化特征

   4.3 逆冲断层失稳的变形场时空演化规律

   4.4 逆冲断层失稳瞬态的滑移位移变化

   4.5 逆冲断层失稳瞬态的声信号变化特征

5 讨论

6 结论