基于塑性损伤的黏土岩力学特性研究

一系列三轴压缩试验表明，黏土岩的力学特性与其应力状态相关。主要表现为：围压越大，黏土岩试样应力峰值越大，且峰值出现得越晚。这是因为高围压试样内部微裂纹闭合趋势更加明显，从而对于微裂纹的发展具有一定的抑制作用。但在软化过程中应力的跌落程度受围压影响不大，这是因为软化过程中，不同围压作用下试样内部的微裂纹均逐渐贯通，并发展成同类型的剪切面，对试样力学性能的削弱大致相同。在试验研究基础上，以微裂纹作为损伤基元，引入受应力状态影响的损伤演化方程（因微裂纹的发展受应力变化影响），建立新的本构模型，通过Abaqus及子程序对新模型进行数值实现。模拟结果与试验结果对比表明，该模型可以有效地描述黏土岩的力学特性。研究成果为黏土岩相关地下工程施工提供了更可靠的理论指导。

Study of mechanical properties of claystone based on plastic damage

Demonstrated by a series of triaxial compression tests, the mechanical properties of claystone are related to its stress state. The relationship between them shows that the larger the confining pressure is, the higher the claystone samples’ peak stress is and the later it develops. This is subject to the tendency of microcrack closure within specimens under high confining pressure, suggesting that high confining pressure has certain inhibitory effects on the development of microcracks. Therefore, the peak stress appears in higher magnitude and at a later stage. However, the degree of the stress drop during the softening process is not heavily affected by the variation of confining pressure. The reason is the microcracks within the samples under different confining pressures gradually connect to each other to generate shear planes of similar type, so that the mechanical properties of the specimens are weakened to the same extent. Based on the experimental study, the paper introduces a damage evolution equation considering varying stress states by taking microcrack as the damage element (because the development of microcracks is affected by stress states). Moreover, a new constitutive model is established based on the test results and numerically implemented in Abaqus and its subroutines. Comparisons between the simulation and experimental results demonstrate the model adequacy for effectively describing the mechanical properties of claystone. The study provides theoretical guidance for the engineering construction of underground infrastructure in claystone.