非贯通裂隙岩体三维复合损伤本构模型

针对非贯通裂隙岩体工程结构中的受荷岩体,提出受荷细观损伤与裂隙宏观损伤的概念。以完整岩石的初始损伤状态作为基准损伤状态,综合考虑裂隙宏观缺陷的存在,微裂纹细观缺陷在受荷下的损伤扩展,以及宏细观缺陷在受荷过程中的耦合,基于Lemaitre应变等效假设,推导考虑宏细观缺陷耦合的复合损伤变量(张量)。给出宏观损伤变量(张量)的计算公式,建立基于宏细观缺陷耦合的非贯通裂隙岩体在荷载作用下的三维复合损伤本构模型,利用试验数据对模型合理性进行验证,讨论不同围压下宏细观缺陷对裂隙岩体力学特性的影响规律。研究结果表明:1工程结构中的受荷岩体,其力学性能由宏观缺陷、细观缺陷以及所处应力状态所决定。单轴应力状态下,岩石力学性质具有明显的脆性,受裂隙几何分布影响较大,具有明显的各向异性。围压状态下,岩石力学性质具有明显延性特征。随围压增加,裂隙岩样的各向异性得到弱化,并趋于各向同性。2裂隙岩样常规三轴压缩试验时,若考虑岩石的压密过程,初始轴向应变在高围压时不能忽略。

3-D constitutive model for rock masses with non-persistent joints based on compound damage

For the rock masses with non-persistent joints under loading in engineering structures, two conceptions are put forward, which are the loaded microscopic damage and the macroscopic damage with joints. Defining the initial damage state of intact rock as the basic state, considering the existence of macroscopic defect with joints, the damage propagation of microscopic defects, micro cracks and the coupling action of macro and micro defects under loading, the compound damage variable (tensor) is deduced based on the Lemaitre strain equivalence hypothesis. The formula for calculating the macroscopic damage variable (tensor) is given, then the three-dimensional damage constitutive model for the rock masses with non-persistent joints under loading is established based on the coupling of macroscopic and microscopic defects. Finally, the test data are adopted to validate this model, and the effects of macro and micro-defects on the mechanical properties of fractured rock masses under different confining pressures are discussed. The research results show that: (1) The mechanical properties of rock masses under loading in engineering structures are determined by the loaded microscopic damage, macroscopic damage with joints and stress state of rock masses. The mechanical properties of rock masses have obvious brittleness and anisotropies under uniaxial stress, and the anisotropies are largely influenced by the geometric distribution of joints. Under confining pressures, the mechanical properties of rock masses have obvious ductileness, and the anisotropies of rock masses decrease and tend to the isotropies with the confining pressure. (2) The initial axial strain of conventional triaxial compression can not be ignored in higher confining pressure if the compaction of rock masses is considered.