循环加卸载下不同冲击损伤砂岩的力学特性研究

Study on the Mechanical Properties of Sandstone with Different Impact Damage under Cyclic Loading and Unloading

针对地下岩体工程在开挖掘进后因循环扰动导致围岩劣化和失稳问题,以冲击损伤砂岩为研究对象,开展三轴循环加卸载试验,研究循环加卸载条件下冲击损伤岩石的性能劣化和破坏规律。研究结果表明,冲击损伤越大的砂岩试样,在临近峰值强度时,其轴向应变会出现急速增长的现象;砂岩的塑性应变随循环次数的增加不断累积,在裂纹不稳定发展阶段,塑性应变大幅度增长;在弹性模量方面,研究发现同一循环等级下,砂岩试样的冲击损伤越大,其对应的割线弹性模量越小,抵抗变形的能力越弱;关于泊松比的研究发现,三种不同冲击损伤砂岩试样在试验过程中都表现出相似的变化趋势,先加速上升,然后缓慢增加,最后急剧增长。但损伤度越大的砂岩试样在试验后期表现出更明显的扩容现象,泊松比增加也更为显著。

In response to the degradation and instability of surrounding rocks caused by cyclic disturbance after excavation in underground rock engineering,a triaxial cyclic loading and unloading test was conducted on impact damaged sandstone as the research object to study the performance degradation and failure law of impact damaged rock under cyclic loading and unloading conditions.The research results indicate that sandstone specimens with greater impact damage exhibit a rapid increase in axial strain near the peak strength;the plastic strain of sandstone accumulates continuously with the increase of the number of cycles,and during the stage of unstable crack development,the plastic strain increases significantly;in terms of elastic modulus,research finds that under the same cyclic level,the greater the impact damage of sandstone specimens,the smaller their corresponding tangent elastic modulus,and the weaker their ability to resist deformation;research on Poisson′s ratio has found that three different types of sandstone specimens with impact damage exhibit similar trends during the testing process:firstly accelerating the increase,then slowly increasing,and finally rapidly increasing.However,sandstone samples with greater damage exhibit more obvious expansion phenomenon in the later stage of the experiment,and the increase in Poisson′s ratio is also more significant.