基于岩石统一能量屈服准则的硬岩损伤模型

A damage model for hard rock based on unified energy yield criterion of rock

为了更准确、便捷地确定深埋地下工程中硬岩的力学行为,开展了如下研究:根据损伤与塑性演化存在相似机制,假设损伤阈值与初始屈服采用相同的确定方法,将岩石统一能量屈服准则作为损伤阈值的判定准则;基于Rabotnov对损伤变量的定义和Lemaitre应变等效性假设,并考虑未损伤部分的应力-应变关系符合广义虎克定律,提出了简化形式的硬岩损伤本构方程;为了更好地表达硬岩从低围压到高围压条件下的脆-延转化特性,提出了改进的Mazars损伤演化方程;基于锦屏T_(2b)大理岩常规三轴压缩试验结果,对损伤模型参数进行求解,并分别与基于Mazars损伤演化方程和Mohr-Coulomb准则为损伤阈值判定准则的损伤模型进行对比,结果表明:提出的损伤模型可更好地表达硬岩从低围压的脆性到高围压的延性转变过程,特别是对损伤阈值后岩石的损伤演化过程的模拟更为精确,对硬脆性岩石的工程计算有一定的借鉴意义。

In order to accurately and conveniently determine the mechanical behavior of hard rock in deep engineering structures, the following works have been conducted in this paper： according to the similar mechanism of damage and plastic, determination scheme of initial yield is assumed to be used for the damage threshold. Unified energy yield criterion of rock is adopted as the decision criterion of damage threshold. Based on the definition of damage variable by Rabotnov and hypothesis of Lemaitre strain equivalence, a simplified damage constitutive law is formulated by assuming the stress- strain relation of undamaged portion to conform Hooke＇s law. Aimed at expressing brittle-ductile transition of hard rock under the condition from low confining pressure to high confining pressure, a modified Mazars damage evolution equation is proposed. Damage model parameters are determined based on conventional triaxial compressive test of T_（2b） marble. The proposed model is contrasted with the model based on Mazars damage evolution and damage threshold criterion used by Mohr-Coulomb criterion respectively. It is suggested that the damage model can express brittle-ductile transition and simulate damage evolution after damage threshold in an accurate way, which has some reference for engineering calculation of brittle hard rock.