基于PMC模型的破坏模式转化型强度准则

进入深部后,受高应力、强扰动影响,岩石岩体中拉断、剪切及压密屈服等破坏模式共生的现象凸显,深部岩石表现出明显地非线性行为,岩石破坏在多种破坏机制中转化。深部岩体强度理论需考虑中间主应力的影响,本文基于Paul-Mohr-Coulomb(PMC)准则,考虑多孔岩石破坏模式间的转化和高围压下裂隙坍塌的特征,提出了在高围压应力情况下,表征压剪屈服的Back-Paul-Mohr-Coulomb(BPMC)模型;推导了BPMC模型摩擦角包络线的表示方法,根据分段线性原则,在p-q平面中获得12边形BPMC线性破坏准则;基于应力不变量在p-q平面的转换关系,利用最小二乘法拟合获得了模型的特征参数。为了验证PMC&BPMC准则及对应破坏模式转化理论的合理性,本文拟合了PMC&BPMC模型,将拟合破坏面与试验数据进行对比;选用四川黄砂岩和金川大理岩,进行多组室内三轴压缩试验,研究不同围压下岩石破坏特征和强度特征,实验采用自主研发的便携式自密封岩石三轴试验高压舱加压系统。对试验数据进行拟合,获得的破坏包络线与实验数据拟合度较好;四川黄砂岩在围压达到90MPa后出现剪应力峰值拐点,产生了孔隙坍塌型破坏,为压屈服破坏。结果表明:PMC&BPMC模型能预测孔隙岩石的帽子屈服面,拟合岩石破坏模式从剪切破坏到压剪破坏的过渡,可预测不同围压下的破坏强度及对应破坏模式。

Destruction mode transformation type strength criterion based on PMC model

After entering deep mine,with the influence of high stress and strong disturbance,various failure modes such as breaking,shearing and compaction yielding are symbiotic in rock mass,the characteristics of nonlinear behavior are obvious,and rock failure mode is transformed in various failure mechanisms.It is necessary to analyze the influence of the intermediate principal stress on the strength theory of deep rocks and rock masses.Based on the Paul-Mohr-Coulomb (PMC) failure criteria,considering the transformation of rock failure mode of porous rock and the pore collapse characteristics,the Back-Paul-Mohr-Coulomb (BPMC) model for characterizing the compression-shear yielding under high stress is proposed.Representation method of the friction angle envelope are derived.According to the piecewise linear principle,a 12-sided BPMC linear failure criterion is obtained in the p-q plane.Based on the transformation relationship between the stress invariants in the p-q plane,the parameters of the model features are obtained with the least-square method.In order to verify the rationality of the PMC & BPMC criterion and the corresponding failure mode transformation theory,a PMC & BPMC model is fitted and compared with the experimental data.Sichuan sandstone and Jinchuan marble are used for high-pressure triaxial compression tests with the portable self-sealing rock triaxial test high pressure chamber system.Fitting the experimental data,the obtained damage envelope and the experimental data have a good fitting degree.The Sichuan yellow sandstone has a shear stress peak inflection point after the confining pressure reaches 90 MPa,resulting in pore collapse type damage,which is the compaction yielding.Experiments are conducted to study the rock failure characteristics and strength characteristics under different confining pressures.The results show that the PMC & BPMC model can predict the cap yield surface of porous rock and the transition of rock failure mode from shear failure to compaction yielding,which can predict the failure strength under different confining pressures.