大理岩脆-延性转换的微观机理研究

Study on microcosmic mechanics for brittle-ductile transition of marble

为探讨高水压对大理岩变形、强度、脆-延转化特性及破坏断裂损伤劣化的影响,取锦屏二级水电站引水隧洞大理岩分别进行高水压、高围压、低围压作用下全应力-应变过程三轴压缩对比试验,对大理岩破坏断裂断口进行微观扫描电镜试验,分析不同工况条件下大理岩断口微观形貌特征.结果表明,在低围压作用下莫尔强度包络线近似为线性,在高围压作用下莫尔强度包络线为非线性.高外水压力的存在抑制了岩石脆性向延性的发展,降低了岩石的强度,对软化区裂纹的扩展起到加剧作用.通过微观数字图像实验分析可知,高围压比低围压条件下大理岩断口裂纹长度小、密度大,分布均匀.给出了高水压、高围压作用下岩石破裂产生的微观损伤力学机理,为进一步分析高围压、高内外水压条件下非圆形洞室围岩失稳破坏提供了可靠的理论依据.

In order to probe into the effects of high hydraulic pressure on the marble characters of strength, deformation, brittle-ductile transition and rupture, damage degradation, the triaxial compression contrastive tests of marble specimens, which were collected from surrounding rocks of diversion tunnel in JinpingⅡwaterpower station, were tested respectively under three different states of high hydraulic pressure and high and low confiding pressure.Then the microtest (SEM) was carried out to study its microcosmic character of failure surface under three different pressure cases.The test results indicate that under low confining pressure Moore strength line is linear, whereas nonlinear under low confining pressure.The existing of high hydraulic pressure constrains the development of brittle-ductile transition, reduces the strength and also makes the effects strongly on the fission cracking in soften area.Based on the testing analysis of microcosmic digital image, there were smaller fissions, larger density and more distribution equality under high confiding pressure than it under low.Microcosmic damage mechanics of rock cracking under high confiding pressure and hydraulic pressure was given, and reliable theory basis was offered to analysis further on the failure and stability of the noncircular cave surrounding rock under high confiding pressure and high hydraulic pressure.