基于本构积分算法的岩体结构面三维弹塑性有限元模型

Three-dimensional elastoplastic model for rock joint elements based on integration algorithm

通过应用非关联塑性理论得到结构面的三维结构面本构关系,定义加载剪涨段和反向剪缩段以适应多方向的复杂加卸载条件,修正以往模型只能剪涨的问题,并考虑了结构面的软化效应。为了这个本构关系能够很好的用于实际工程的有限元计算,结合ABAQUS二次开发功能,编制了UEL用户自定义单元子程序。算法采用后退Eular法,以避免在有限元计算中出现应力状态偏离屈服面的情况,提出了基于本构积分算法的结构面单元,以及与其一致的算法模量,应对不平滑的屈服面展示了良好的收敛性和计算速度。最后进行数值实验,分别模拟了直剪实验,循环剪切实验和约束刚度实验。通过与实验结果的比较,确认了模型的合理性。

The mechanical behaviours of rock mass of major civil engineering are dramatically affected by the presence of joints,and the major discontinues can cause a variety of problems in both surface and underground constructions.Realistic simulation of the mechanical behaviours of rock joints becomes an important part of modelling the rock mass.A three-dimensional joint element based on the framework of elastoplastic constitutive model is proposed to account for dilatancy,roughness and undulating surface of discontinuities.To simulate the behaviours of joints under complex loading condition,dilatancy and reduction zone are suggested.An integration algorithm of constitutive equations based on the Euler backward integral method is used,and the consistent tangential matrices are derived.An ABAQUS user-defined element subroutine using this model is programmed,three experiments of direct shear tests,cyclic shear tests and restricted normal stiffness shear tests are simulated by ABAQUS,and the calculated results are analyzed to verify this method.