三轴压缩下红砂岩峰后应力松弛特性试验研究

Experimental Investigation on Post-Peak Relaxation of Red Sandston under Triaxial Compression

为揭示岩石峰后松弛特性,采用MTS815电液伺服试验机,对红砂岩进行了三轴压缩下峰后松弛试验,分析了峰后松弛曲线特征,研究了损伤程度、位移加载速率对峰后松弛的影响规律,探讨了围压、初始应力水平对峰后松弛特性的影响机理.试验结果表明:制约红砂岩峰后松弛试验成功进行的因素包括岩样的损伤程度、位移加载速率等;增大位移加载速率能在一定程度上延长红砂岩岩样峰后松弛失稳时间,减小损伤程度能使峰后松弛以衰减松弛为主,很快趋于稳定;红砂岩峰后松弛曲线主要由瞬时松弛段和减速松弛段组成;应力松弛量与围压、损伤程度以及初始应力有关,与围压呈负相关,与损伤程度、初始应力呈正相关.研究结果对于岩石峰后流变特性研究及破裂围岩控制具有一定的意义.

In order to reveal the post-peak relaxation properties of rock, the post-peak test of red sandstone under triaxial compression is carried out to analyze the characteristics of the post-peak relaxation curve, study the influence law of post - peak relaxation characteristics with the items of the damage degree of rock and displacement loading rate, and discuss the influence mechanism of post - peak relaxation characteristics with confining pressure and initial stress level by using the MTS815 electro-hydraulic servo testing machine. Through the researches, the following results are achieved. The factor of restricting on the success of the red sandstone post-peak relaxation test includes the damage degree of rock samples, displacement loading rate, etc. Increasing the displacement loading rate can prolong relaxation instability of cracked rock samples to a certain extent. After reducing the damage degree, the post - peak relaxation was dominated by attenuation relaxation, and soon stabilized. The post-peak relaxation curve is mainly composed of instantaneous relaxation stage and deceleration relaxation stage. The post - peak stress relaxation is negatively correlated with the confining pressure, but positively correlated with the degree of injury and initial stress. The research results have some significance for the study of rheological characteristics of rock post-peak and the control of the cracked surrounding rock.