双轴压缩试验下岩石裂纹扩展的离散元分析

DISCRETE ELEMENT ANALYSIS OF CRACK PROPAGATION IN ROCKS UNDER BIAXIAL COMPRESSION

基于颗粒离散元理论,研究含2条预制裂纹的Hwangdeung花岗岩在双轴压缩试验下的裂纹扩展及破坏模式。研究结果表明:围压对岩石裂纹扩展及破坏模式有显著影响;水平预制裂纹对倾斜预制裂纹的保护作用随着围压的增大而增强;且倾角越大,水平预制裂纹的保护作用越明显;当预制裂纹倾角α≤75°时,试验停止时微裂纹数目随围压的增加而增大;而当预制裂纹倾角α=90°时,微裂纹数目先增大后减小;试样的起裂应力都随着围压的增加而增大(除α=75°);试样的峰值强度也均随着围压的增大而增大;预制裂纹倾角不同,围压对试样的起裂应力和峰值强度的影响程度不同;相同围压下,不同预制裂纹倾角试样的起裂应力和峰值强度的大小关系无明显规律,而与其具体破坏模式有关;整体来看,当预制裂纹倾角α=60°时,围压对岩体力学特性影响最大。

Based on the theory of particle discrete element,the crack propagation and failure mode of Hwangdeung granite with two pre-existing flaws are researched under biaxial compression. The results show that confining pressure has a significant effect on crack propagation and failure mode. The effect of the horizontal flaw shielding the inclined flaw from a vertical load enhances with the increase of confining pressure. And the larger flaw inclination angle is,the more obvious the protective effect is. When flaw inclination angleα≤75° ,the number of microcracks increases with the increase of confining pressure at the end of tests. Whenα=90°,the number of microcracks firstly increases and subsequently decreases with the increase of confining pressure. Crack initiation stress of rock specimen increases with the increase of confining pressure exceptα=75°. Peak strength of rock specimen also increases with the increase of confining pressure. Confining pressure has different effects on crack initiation stress and peak strength of rock specimen with different flaw inclination angles. The size relation of crack initiation stress and peak strength of rock specimen with different flaw inclination angles exhibits no clear increasing or decreasing trend under the same confining pressure,for they are related to failure modes of rock specimen. On the whole,confining pressure has the largest impact on the mechanical properties of rock specimen with flaw inclination angle of 60°.