裂纹延伸扩展过程中的受力状态分析

Research on Stress State of Rock Crack Extending

对含45°预制裂纹的花岗岩板进行单轴压缩实验,采用电阻应变计监测裂纹延伸扩展过程中的受力状态。结果表明:翼形裂纹是单纯受到拉伸应力作用产生的,而二次裂纹是受到剪切作用产生的,表现为拉压应力交替作用,但在二次裂纹扩展的不同阶段,所受到的主要应力不同,在二次裂纹刚开始扩展时压应力是主要应力,随着二次裂纹的延伸扩展,拉应力成为了主要应力;引起二次裂纹扩展的剪切应力区域比引起翼形裂纹扩展的拉伸应力区域宽泛得多;受挤压作用产生的裂纹,实质上是由受压引起的剪切型张拉应力迫使其开裂的。

The stress state of rock crack extending was studied in the uniaxial loading test of the granite plate with 45°preexisting crack, in which stress state was monitored by resistance strain gage. The results show that wing crack is generated simply by tensile stress, but secondary crack is generated by shear stress, showing the role of alternating tension and compression stress. In different stages of the secondary crack extending, the main stress is different. In the beginning of the secondary crack extending, the main stress is compression, but with the secondary crack extending, tensile stress becomes the major stress. The region of the shear stress which generates the secondary crack is much broader than the tensile stress which generates the wing crack. The crack generated by compression is essentially generated by the tensile stress which is caused by compression.