地下工程围岩承受载荷的形式为真三轴卸–加载后的扰动载荷,在频繁扰动载荷作用下围岩易出现物理力学性能劣化,进而诱发岩爆等工程灾害。基于地下工程围岩复杂受力环境,利用自制的岩石真三轴扰动诱变试验系统,开展复杂真三轴预应力路径和局部异源扰动载荷作用下花岗岩破裂试验。试验结果表明,在特定的应力状态下,在较大幅值的局部异源扰动载荷下花岗岩发生剧烈破坏,破裂模式为劈裂拉伸破坏。利用PFC3D精确再现室内试验并研究岩石扰动破裂的微观机制,研究结果表明:岩石内部的颗粒黏结从扰动载荷作用处开始破坏,当扰动载荷的幅值为150,200,250 k N时,破坏颗粒黏结数趋于稳定,最终岩石未发生整体破坏;但扰动载荷幅值等于300 k N时,破坏黏结数从施加扰动载荷位置扩散至试件整体,岩石扰动破坏由剪切破坏逐渐转变为拉伸破坏,最后发生试件整体破坏,室内试验与数值模拟结果相一致。
The mechanical properties of red sandstone subjected to cyclic point loading were investigated. Tests were conducted using MTS servohydraulic landmark test system, under cyclic loadings with constant amplitudes and increasing multi-level amplitudes. The frequencies range from 0.1 to 5 Hz and lower limit load ratios range from 0 to 0.60. Laboratory investigations were performed to find the effect of the frequency and the lower limit load ratio on the fatigue life and hysteresis properties of sandstone. The results show that the fatigue life of sandstone decreases first and then increases with the increase of frequency and lower limit load ratio. Under the same cycle number, the spacing between hysteresis loops increases with rising frequency and decreasing lower limit load ratio. The existence of “training” and “memory” effects in red sandstone under cyclic point loading was proved.
