三轴压缩下红砂岩峰后蠕变力学特性试验

Experimental Study of Post-peak Creep Mechanics Characteristics of Sandstone Under Triaxial Compression

为研究岩石峰后蠕变力学特性,利用MTS815电液伺服岩石力学试验系统,对红砂岩进行三轴压缩下峰后蠕变试验.分析了红砂岩峰后蠕变特征,估算了红砂岩峰后长期强度,采用改进的西原模型对峰后蠕变特性进行了描述,确定了模型参数.结果表明:红砂岩峰后蠕变破坏应力下并不直接进入加速蠕变阶段,而是由等速蠕变阶段逐渐向加速蠕变阶段转化.红砂岩峰后蠕变变形主要集中于加速蠕变阶段,加速蠕变阶段短时间内蠕变的剧烈变形是岩石失稳破坏的重要原因.随着荷载的加大,岩样的破坏形态由单一的剪切破坏与裂纹扩展等破坏形式逐渐向多剪切破坏演化,破坏块体增多,岩样更加破碎.本次试验红砂岩峰后长期强度仅为其峰值强度的42.56%,长期强度折减量较大.红砂岩峰后蠕变特性可用改进的西原模型进行描述,各级应力水平下模型曲线与试验曲线拟合较好.研究结果为深部工程围岩峰后流变力学特性研究提供了一定的参考意义.

In order to study the post-peak creep mechanical characteristics of rock,the triaxial post-peak creep test of red sandstone was carried out by applying the MTS815 electro-hydraulic servo rock mechanics test system.The post-peak creep characteristics of red sandstone was analyzed,and the post-peak long-term strength of red sandstone was estimated based on creep test.The post-peak creep characteristics were described by the improved Nishihara model,and the model parameters were determined.The results show that the post-peak creep of red sandstone under failure stress is not directly into the accelerated creep stage,but the transition from the constant creep stage to the accelerated creep stage.The post-peak creep deformation of red sandstone is mainly concentrated in the accelerated creep stage,and the rapid deformation of creep during the accelerated creep stage is the important reason for the rock failure.With the increase of the load,the failure modes of rock samples are gradually evolved from multiple shear failure and crack propagation to multiple shear failure.Destruction of the block increases and tends to break.The post-peak long-term strength of red sandstone is only 42.56%of its peak intensity for the test,and the long-term strength significantly reduces.The post-peak creep characteristics of the red sandstone can be described by the improved Nishihara model,and the model curve is better fitted with the test curve under all the stress levels.The results provide a reference for the study of the post-peak rheological mechanical behavior of the surrounding rock in deep engineering.