三向应力下典型岩石破坏预警及峰后特性

为探讨岩石在三向应力下的变形、破坏规律及其峰后本构模型,对不同围压下石灰岩和砂岩进行了三轴压缩全过程试验,分析了2种典型岩石的变形、破坏规律和峰前、峰后承载能力与变形之间的关系,在此基础上建立了岩石的本构模型.研究结果表明:石灰岩在低围压下易于发生失稳破坏,在高围压下较难发生失稳破坏,围压的增大对岩爆有一定抑制作用;同种岩石峰值应力时对应的环向应变不随围压的改变而改变,近似为一定值,可以将其作为岩石破坏的一个预警指标;石灰岩的剪胀效应发生在破坏后,而砂岩在轴向应力达到其峰值的70%左右时就开始出现剪胀;岩石峰后应力与其承载能力相等,由侧向变形控制,随侧向变形增大逐渐衰减至残余强度;基于本构模型的计算结果与三轴压缩试验结果吻合较好.

Failure Prediction and Post-Failure Behavior of Typical Rock under Triaxial Compression

In order to research the failure prediction and post-failure constitutive model of rock under triaxial stress,the triaxial compression tests of limestone and sandstone were conducted under different confining pressures,the regularities of deformation and failure and the relationship between strength and deformation in the whole loading process were analyzed.Based on the test result,a constitutive model for rock was founded.The research results show that the failure mode of limestone is stability loss under a low confining pressure condition,and high confining pressure can restrain rock burst to some extent.The circumferential strain corresponding to the peak stress is nearly a constant under different confining pressures,as a result,it can be taken as an index of rock failure prediction.The shear dilatancy occurs in the post-failure to limestone and at the moment when the axial stress reaches 70% of the peak stress to sandstone.The stress of rock is equal to its strength in the post-failure state,controlled by the lateral deformation,and decreases to the residual strength as the lateral deformation increases.The calculational results based on the constitutive model are consistent with the experimental results under triaxial compression.