膏岩三轴压缩声发射特征及损伤演化研究

利用MTS 815岩石力学测试系统对膏岩进行不同围压下的三轴压缩试验,配合AE系统进行全过程声发射监测,展开了膏岩变形破坏过程的力学特性及声发射特征进行研究,并进一步探讨膏岩变形破坏过程损伤演化规律。试验结果表明:(1)膏岩是一种致密低渗岩石,气体孔隙度在1.30%~3.50%之间;(2)三轴加载条件下,膏岩的力学性质与声发射参数对围压的响应效果强烈,50 MPa围压较5 MPa围压下膏岩强度提高110.67%。高围压下声发射信号表现出明显的“滞后”效应,声发射集中分布区不断向后推移;(3)膏岩的临界围压为20 MPa。低围压下膏岩呈脆性破坏,破坏后形成宏观剪切面;临界围压下呈塑性破坏,破坏后形成共轭Y型剪切;高围压下呈延性破坏,破坏形态为鼓胀破坏;(4)膏岩损伤演化过程可分为初始损伤期、损伤快速发展阶期与损伤平稳期,能够与膏岩变形破坏阶段对应;损伤快速发展期为膏岩内部裂隙发展、贯通的主要阶段。

Investigation on Deformation Characteristics and Damage Evolution of Gypsum Rock under Triaxial Loading Test

Triaxial compression test for gypsum under different confining pressure were conducted using MTS 815 testing machine, with the AE system monitoring to investigate the mechanics properties and acoustic emission (AE) characteristics for gypsum during deformation and failure process. And the damage evolution law of rock deformation and failure process were further discussed. The test results show that:(1) the gypsum is a dense and low-permeable rock with gas porosity of 1.30%~3.50%. (2) mechanical properties and acoustic emission parameters of the gypsum have a strong response to confining pressure under triaxial compression, and strength increases by 110.67% at the confining pressure of 50 MPa than that of 5 MPa. Acoustic emission signals pressure show obvious "lag" effect under high confining, and the concentrated distribution area of acoustic emission keeps moving backward. (3) the critical confining pressure of the gypsum is 20 MPa. Under low confining pressure, brittle failure and macroscopic shear plane of gypsum specimens is noted. Plastic failure occurs under critical confining pressure and conjugate Y-shape shear is formed after the failure. Ductile failure occurs under high confining pressure and the failure pattern is swelling. (4) the damage evolution of the gypsum can be divided into three stages: initial damage stage, rapid damage development stage and the stable damage stage, which is in agreement with the deformation and failure process of the gypsum. And the rapid damage development stage is the main stage for the initiation and propagation of cracks in the gypsum.