基于宏细观损伤耦合的非贯通裂隙岩体本构模型

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，推导了考虑宏细观缺陷耦合的复合损伤变量，并给出同时考虑试件尺寸、裂隙几何与力学特性的宏观损伤变量的计算公式，从而建立了基于宏细观缺陷耦合的非贯通裂隙岩体在荷载作用下的损伤本构模型。用宏细观损伤耦合的本构模型来描述非贯通裂隙岩体在受荷过程中的细观损伤演化与宏观损伤行为，与非贯通裂隙岩体实际受荷情况符合较好。研究结果表明：（1）完整岩样和裂隙岩样的应力-应变行为在峰值强度之前差异较大，峰值强度以后差异逐渐减小，最后趋于一致，二者具有相近的残余强度；（2）裂隙岩体强度随裂隙贯通率的增加而增大，随裂隙倾角的变化具有明显的各向异性，同时还与裂隙面的内摩擦角有关；（3）裂隙倾角为90°时，裂隙岩样的峰值强度最高；张开型裂隙岩样的裂隙倾角为45°时，峰值强度最低；（4）非贯通裂隙岩体工程结构中的受荷岩体，其力学性能由受荷细观损伤与裂隙宏观损伤及其耦合效应所决定，基于宏细观损伤耦合的复合损伤变量可以较好地反映非贯通裂隙岩样的力学特性。

Constitutive model of rock mass with non-persistent joints based on coupling macroscopic and mesoscopic damages

To study characteristics of rock mass with non-persistent joints under loading in engineering structures, two conceptions are put forward, which are mesoscopic damage of loading and macroscopic damage with joints. The initial damage state of intact rock is defined as a basic state. A compound damage variable is deduced on the basis of the Lemaitre strain equivalence hypothesis, which considers the existence of macroscopic defect with joints, the damage propagation of mesoscopic defects, micro cracks, and the coupling actions of macro and meso-defects under loading. A new calculation formula of the macroscopic damage variable is derived simultaneously in terms of the specimen size, geometrical size of joints and mechanical properties of joints. Then, a damage constitutive model for rock mass with non-persistent joints is established based on coupling macroscopic and mesoscopic defects. This paper describes the evolution of mesoscopic damage and the behavior of macroscopic damage of rock mass with non-persistent joints under loading. The calculated results are in good agreement with the actual failure of rock mass. The results show that: (1) The stress-strain behaviors of fractured and intact rock samples show a significant difference prior to the peak strength. The difference gradually decreases after the peak strength. Finally, the residual stress tends to be equal. (2) The strength of fractured rock mass increases with the joint connectivity rate, and exhibits obvious anisotropy with the variation of joint inclination angle, and also is relevant to the internal friction angle of joints. (3) The peak strength of fractured rock samples is the highest at the joint inclination angle of 90°. While the peak strength is the lowest at the joint inclination angle of 45°for open-type fractured rock samples. (4) The mechanical properties of rock mass under loading in engineering structures are determined by the mesoscopic damage of loading, macroscopic damage with joints and their coupling effects. The coupling macroscopic and mesoscopic based compound damage variable may well characterize mechanical properties of rock mass with non-persistent joints.