标题：Experiment on formation mechanism of rock class II curve
作者：Chen, Shao-Jie ;Guo, Wei-Jia ;Liu, Jin-Xiao ;Yin, Li-Ming
作者机构：[Chen, Shao-Jie ;Guo, Wei-Jia ;Liu, Jin-Xiao ;Yin, Li-Ming ] Key Laboratory of Mine Disaster Prevention and Control, Shandong University of Science an 更多
来源：Meitan Xuebao/Journal of the China Coal Society
摘要：Several typical sedimentary rocks' class II curves were obtained by combined loading control mode of axial-dis & circumferential-dis on MTS test system, and the formation mechanism of class II curve was analyzed based on test results. The occurrence of class II curve needs two conditions. The first is appropriate loading mode. The circumferential displacement should be used as the loading control variable slowly in sample failure process. Second, the rock possesses brittleness property and can amass some flexibility energy. Only the variable with max change rate is used as the loading control parameter in different stages of the whole stress-stain curve, the class II curve may be obtained. While sample turn into post-peak phase of class II curve, the flexibility energy amassed in itself can lead it break down, and the circumferential displacement increases rapidly without loading. At this time, if the loading rate of circumferential displacement is less than the change rate caused by its broken down, the MTS will unload. At the same time, the sample failure caused by flexibility energy releasing makes the circumferential strain increase and the axial strain reduce. Rock samples with the same mechanical properties are characterized as Class I or II, which are controlled by different loading control mode.