岩石卸荷破坏的变形特征及本构模型

Failure characteristics and constitutive model of rock under unloading condition

对闪长岩试样进行了加轴压、卸围压试验,研究了卸荷条件下闪长岩的变形和破裂特征.结果表明:与加载试验相比,卸荷试验中岩样轴向应变没有明显的应变强化过程,轴向应变峰值较小,弹性模量与围压呈非线性关系降低,泊松比与围压呈非线性关系增加,岩样破坏特征以主剪切破坏为主.基于试验认识,采用损伤力学理论,通过岩石强度的随机分布假设和摩尔-库仑强度理论,引入比例系数,建立了一个能够反映岩石卸荷特征的三维损伤本构模型.基于试验结果给出模型参数,模型能够反映岩石卸荷条件下的强度及脆化特征,理论结果和试验结果吻合较好.

The full stress-strain curves and deformation features of rocks were obtained based on the results of triaxial unloading tests. The results show that compared with loading condition, the axial strain harden stage is shorter for unloading, the axial peak strain is lower. Deformation modulus decrease and Poisson ratio increase in the process of unloading. Primary shear failure is the main failure modes of rocks. Based on experimental results, a three-dimensional rock damage constitutive model was established by using Weibull distribution and Mohr-Coulomb theory. The model agrees well with experimental results, which reflect the change of strength with confining pressure and characteristic of brittle of rock under unloading condition.