低围压下脆性岩石单裂纹扩展与影响因素分析

为了探究低围压下脆性岩石单个裂纹扩展与影响因素,开展了混合片麻岩室内岩石力学基本实验,确定了Sheorey强度准则参数;利用岩石滑动裂纹模型和非局部线弹性理论,在综合分析裂纹尖端应力场包括非奇异应力项的基础上,建立了混合片麻岩单裂纹扩展USR判据。理论分析认为:脆性岩石单个裂纹扩展过程分为缓慢、中等和加速3个阶段,并且裂纹逐渐向最大竖向压力方向扩展;影响因素分析表明:(1) 随着裂纹摩擦系数和裂纹倾角增大,竖向应力随着裂纹扩展而增大;(2) 当侧压力为拉应力时,竖向应力随着裂纹扩展而减小;当侧压力为压应力时,随着测压力系数增大,竖向应力随着裂纹扩展而增大;(3) 随着初始裂纹长度增大,竖向应力随着裂纹扩展而减小。

Analysis on Single Crack Propagation and Its Influence Factors of Brittle Rock under Low Surrounding Pressure

It is necessary to understand the single crack propagation process and its influencing factors of brittle rock under low confining pressure. The basic rock mechanics experiments of mixed gneiss are carried out in the laboratory, then the parameters of Sheorey strength criterion are obtained. The rock sliding crack model and non local linear elastic theory are adopted and USR criterion for single crack propagation of mixed gneiss is established based on the comprehensive analysis of the stress field at the crack tip including the non singular stress term. Theoretical analyses show that crack propagation process of brittle rock is divided into three stages: slow stage, medium stage and accelerated stage, and the crack gradually propagates to the direction of the maximum vertical pressure. Analyses of influencing factors also show that: (1) the vertical stress increases during crack propagation with the increasing of friction coefficient and inclination angle of crack; (2) the vertical stress decreases during crack propagation when the lateral pressure is tensile; with the increasing of coefficient of lateral pressure, the vertical stress increases during crack propagation when the lateral pressure is compressive; (3) the vertical stress decreases during crack propagation with the increasing of initial crack length.