非均匀性岩石破裂的网格效应

MESH EFFECTS ON FAILURE PROCESSES OF HETEROGENEOUS ROCKS

主要在考虑岩石介质非均匀性的基础上。研究岩石破裂过程中的网格尺寸效应。首先，介绍RFPA软件中网格划分特点和裂纹扩展处理方法，讨论非均匀性对预制裂纹扩展的影响；然后，模拟两组结构相同但网格数目和尺寸不同的岩石材料的破裂过程。分析在非均匀性岩石中单元尺寸对于岩石破裂过程的影响。结果表明，在均质度较高的岩石试件中，岩石强度相对高，并且裂纹扩展表现出很强的脆性：随着网格数目的增加和网格尺寸的减小，岩石强度逐渐降低，并且趋向一个稳定值。考虑到岩石的非均匀性后的破坏过程分析必额考虑由破坏0f起的应力重新分布，且单元尺寸满足一定的细观特征尺度后，才能保持破裂分析的稳定性和可靠性，体现破裂过程分析和应力场和位移场分析的不同之处。在均匀条件假设下，网格的尺寸主要和结构特征相关，但是在非均匀介质中，网格的尺寸还与材料的非均匀性和细观特征尺度密切相关。

The purpose of this paper is to study the mesh size sensitivity in rock progressive failure process by taking heterogeneity into consideration. The size of crack tip in the plastic zone is obtained by using classical elasto-plastic theory. Then two numerical models containing a pre-existing crack are conducted to uniaxial compressive loading to investigate the homogeneity effects. Two numerical specimens are divided into the same grid meshes and they have same geometry and size but different heterogeneity. In the other way, four numerical models with the same geometry and size are divided into different meshes to study the mesh sensitivity. Numerical analysis results show that the peak strength of the rock specimens increases as homogeneity increases and crack propagates smoothly until brittle fracture takes place. It also approves that the mesh size should be small enough to fit the need of failure process analysis if the heterogeneities are taken into account in rocks. Mesh size has great dependence on the structural property in homogeneous materials, while mesh size depends on the degree of heterogeneity of the material as well as structural property in heterogeneous materials. Mesh geometry and mesh size adjustment during crack propagation process should be based on the assumption that materials are homogenous.