岩石节理多层结构模型研究

Research on hierarchical model of rock joints

为了研究节理细观形态对其宏观力学性状的影响,据岩石节理分形特点,将节理面分解为不同层次细观结构面,节理破坏拟为粗糙度分层渐进破坏的过程,基于Plesha本构建立了岩石节理多层结构模型.模型将粗糙度定义为等效起伏角,力学响应发生在最底层(基本面),结构面受力性状由下层结构面平均化得到,基本面破坏后,其上层结构面转化为基本面.模型考虑了弹性变形、滑动变形、磨损、剪断、压碎、分离等作用机理,能模拟剪胀、应变软化等现象,能考虑单调及循环剪切效应.采用ABAQUS的用户子程序UEL进行了模型验证与参数分析.计算表明:峰值剪切应力随着结构层次的增加而增大;在结构层次不变时,等效峰值摩擦系数随法向应力的增大而减小;剪切应力终值由基本摩擦角控制;剪应力-位移曲线形态取决于粗糙度结构特性;模型中刚度系数对剪切性状影响很小.

Joint behaviors was related to its microscopic morphology.Therefore,a hierarchical model was proposed based on the fractal characteristic of rock joints.According to this model,the roughness of rock joints was represented by asperity angle,joints macro-asperity angle was decomposed into different level of micro-asperity angle,the surface with the lowest level asperity angle（also as basic surface） control joint performance through homogenization,after the basic surface was broken down,the surface with the second lowest level asperity angle converted to the basic surface,joints failed progressively from the lower level to higher level.Model verification and parameters sensitivity analysis were carried out by the UEL of commercial soft package ABAQUS.Results show that this model can simulate the mechanism of elastic deformation,sliding,damage,shear-off,crush and separation of rock joints,the peak shear stress increase with the number of micro-asperity level,the peak equivalent friction coefficient decrease with the increasing normal stress when the micro-asperity level unchanged,the final shear stress is attributed to the basic friction angle,the curve shape of shear stress versus shear displacement is affected by the magnitude of damage coefficient and the stiffness have little influence on the shearing behaviors of rock joints.