循环荷载下岩体结构面本构关系与积分算法研究

地下结构中广泛存在的各种不连续面是影响岩体工程力学特性的重要因素,研究结构面在循环荷载作用下的力学行为具有重要的工程意义。基于非关联塑性理论,同时定义加载剪胀段和反向剪缩段,建立了岩体结构面剪胀与塑性耦合本构关系;从结构面的基本损伤机制出发,基于拉、剪分离的思路,建立了一类基于能量原理的岩体结构面拉、剪损伤本构模型,该模型基于有效应力空间塑性力学基本原理,定义了岩体结构面拉、剪塑性Helmholtz自由能分量及损伤能释放率,建立了岩体结构面拉、剪损伤破坏准则。针对结构面在循环荷载作用下的强非线性问题,引入算子分解的思想,将弹塑性演化与损伤演化过程分开进行求解,提出了结构面弹塑性损伤本构关系的混合积分算法。分别进行了岩体结构面直剪和循环剪切试验的数值仿真,计算结果与模型试验基本一致,表明该模型在模拟非连续岩体复杂变形方面是合理有效的。

Constitutive relation and integration algorithm for rock discontinuities under cyclic loading

The discontinuities distributed in underground structures are the important factors that affect the mechanical characteristics of rock mass, and to study the mechanical behavior of rock discontinuities under cyclic loading is of great engineering significance. In light of the non-associated plastic theory, defining the dilatancy and reduction zones, a constitutive model for rock discontinuities considering the coupling of dilatancy and plasticity is established. Starting from the basic damage mechanism, with regard to the separation of tension and shear, a new damage constitutive model based on the energy theory is proposed. In which the tension and shear plastic Helmholtz free energy and damage energy release rates are determined by using the basic principle of plastic mechanics in the effective stress space, and the tension and shear damage failure criteria for rock discontinuities are proposed. Aiming at the strong nonlinear performance of rock discontinuities under cyclic loading, the operator decomposition method is introduced. The coupling process of dilatancy and plasticity, as well as the damage evolution process, is solved separately, and a mixed integration algorithm for the elastoplastic damage constitutive relation of rock discontinuities is put forward. Some experiments of direct shear and cyclic shear are simulated respectively, and the agreements between the simulated results and the experimental data indicate that the proposed model is reasonable and effective to simulate the complex deformation of discontinuous rock mass.