脆性砂岩预制裂隙扩展破坏过程试验研究

摘要

The propagation and failure process of rock fracture under uniaxial compression was studied by using the CSS-3940YJ rock mechanics test machine.Based on the experimental results of the complete deformation curves,the effect of crack dip angle on the deformation,strength and crack propagation failure mode of rock were analyzed.The result of research showed that compared with the complete sample,the prefabricated crack deformation of sandstone showed the characteristics of asymptotic damage localization,the peak strength and the peak axial strain were significantly lower.As the increasing of prefabricated crack dip angles,the decreased magnitude was decreased.We found the macroscopic failure mode of rock samples mainly presented three kinds of pull failure,shear failure and mixed damage and the transition from shear to pull was gradually increased with the increase of crack dip angle.It worths pointed out that the process of loading was in a state of stress concentration on both ends of the prefabricated crack,so that both ends of the prefabricated crack came out of the wing type crack perpendicular to the crack and the direction of loading force came to the development on both ends of the sample.Then prefabricated cracks produced the wing type crack prefabricated crack and secondary coplanar shear crack.The more secondary cracks occurred in the fracture angles,the more complicated the fracture mode of the rock sample.%采用CSS-3940YJ岩石力学试验机,开展单轴压缩条件下岩石预制裂隙扩展破坏过程试验.基于全程变形曲线的试验结果,分析了裂隙倾角对岩石变形、强度、裂隙扩展破坏方式的影响规律.研究结果表明,与完整岩样相比,预制裂隙砂岩变形呈现出局部化渐近破坏特征,其峰值强度、峰值轴向应变均明显降低,且降低幅度随着预制裂隙倾角的增大而减小;岩样宏观破坏模式主要呈现出拉破坏、剪破坏和混合破坏3种,且随着倾角的增加逐渐由剪向拉破坏过渡.值得指出的是:由于在加载过程中预制裂隙两端处于应力集中状态,导致在预制裂隙两端会首先萌生出垂直于裂隙的翼型裂纹,并沿着加载力方向向岩样两端发展,随后在预制裂隙两端会产生反翼型裂纹和次生共面剪切裂纹,裂隙倾角越小产生的次生裂纹数目越多,岩样的贯通破坏模式就会越复杂.