中主应力对内嵌π平面裂纹扩展行为的影响

采用简化的增强虚内键(AVIB)本构模型,利用三维单元劈裂法对真三轴作用下内嵌π平面裂纹的扩展过程进行了数值模拟,得到了三维应力下内嵌裂纹的扩展模式和裂纹体强度变化规律.结果表明:在真三轴应力作用下,微裂纹从预置裂纹两侧开始起裂,沿着最大主应力方向扩展,形成一个倾斜的"马蹄形"包裹状裂纹,随着中主应力的增加,"马蹄形"包裹状裂纹逐渐向中主应力方向发生扭转;当中主应力较小时(约小于单轴强度的50%),裂纹体峰值强度随中主应力的增加几乎呈线性增长;当中主应力增至一定值时(约为单轴抗压强度的80%),裂纹体峰值强度达到最大,随后三轴抗压强度随着中主应力的增加而减小.文中的研究结果为高地应力作用下的内嵌平面裂纹扩展规律的分析提供了有意义的参考.

Influence of Intermediate Principle Stress on Embedded π Plane Crack Propagation

To explore the influence of the intermediate principle stress on embedded crack propagation, the simplified Augment Virtual Internal Bond (AVIB) model in conjunction with the three dimensional element partition method was used to simulate the propagation process of an embedded π plane crack subjected to true triaxial stress. The simulation results suggest that the fracture first initiates at the tip of the pre existing planar crack and then propagates in wrapping mode along the maximum principle stress. With the increase in intermediate principle stress, the “wrapped” extended crack rotates to the direction of the intermediate principle stress. The triaxial compressive strength of rock is also related to the intermediate principal stress. When the intermediate stress is smaller than a certain value (approximately 0.5σc), the triaxial compressive strength almost grows linearly with the intermediate principal stress. After the t intermediate principal stress exceeds a certain value (approximately 0.8σc), the triaxial strength decreases with intermediate stress increasing. The simulated results provide valuable reference for the analysis of embedded planar crack propagation in rock under high compressive in situ stress. Key words：