高静应力与低频扰动耦合作用下砂岩的力学响应特征

Mechanical response of sandstone under coupling action of high static stress and low frequency disturbance

低频扰动荷载作用下高应力状态岩石的力学响应特性是残采区上行开采层间岩层稳定性的重要影响因素。基于自主研发的动静载耦合电液伺服试验机,开展动静载耦合作用下高应力状态砂岩巴西劈裂试验,分析低频扰动荷载幅值对高静应力砂岩力学响应特征的影响。结果表明:(1)高应力状态砂岩不会在小幅扰动荷载作用过程中破坏,但扰动损伤会降低岩样抗拉强度,基于层间岩层静态力学特性的上行开采稳定性分析中应纳入合适的折减系数;(2)高静应力砂岩破坏前的扰动荷载循环次数随幅值升高而降低,幅值为5.0、7.5、10 kN组岩样破坏前的扰动荷载循环次数均值分别为157、70、3;(3)引入描述流体状态的“紊流”形象化表达扰动荷载作用过程中附加能量的快速输入与输出,呈“紊流”状态的附加能量弱化了砂岩裂纹扩展的有序性,诱使砂岩破坏瞬间发生大规模裂纹扩展。该研究成果可为残采区上行开采稳定性分析提供一定参考。

The dynamic response of rock in high stress state under low-frequency disturbance load are important factors affecting the stability of interlayer strata during upward mining in residual mining area. Brazilian splitting test on sandstone in high stress state under dynamic and static load coupling was carried out using the self-developed dynamic and static load coupling test machine. The effect of low frequency disturbance load amplitudes on the mechanical response characteristics of high static stress sandstone was analyzed. The results show that: 1) The sandstone in high stress state will not be destroyed in the process of small disturbance load,but the disturbance damage will reduce the tensile strength of rock specimens. Therefore, the appropriate reduction factor should be introduced into the upward mining stability analysis based on the static mechanical parameters of interlayer rock. 2) The fatigue life of sandstone decreases with the increase of the amplitude of the disturbance load. The average number of dynamic load cycles before failure of the sandstone subjected to the load the amplitude of 5.0, 7.5 and 10 kN is 157, 70 and 3, respectively. 3) The “turbulence”describing the fluid state is introduced to visualize the fast input and output of additional energy in the process of disturbance load.The additional energy flow in the state of “turbulence” weakens the orderliness of sandstone crack propagation, and induces large-scale crack propagation at the moment of sandstone failure. The research results can provide certain reference for the stability analysis of upward mining in residual mining area.