高围压高水压条件下大理岩断口微观机理分析与试验研究

EXPERIMENTAL STUDIES AND MICROCOSMIC MECHANICS ANALYSIS ON MARBLE RUPTURE UNDER HIGH CONFINING PRESSURE AND HIGH HYDRAULIC PRESSURE

为了探讨高围压高水压对大理岩变形、强度、脆–塑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,然后,对大理岩破坏断裂断口进行微观电镜扫描试验,分析不同工况条件下大理岩断口微观形貌特征。试验结果表明,在低围压作用下莫尔强度包络线近似为线性的,在高围压作用下莫尔强度包络线是非线性的。高水压力的存在抑制岩石脆性向塑性的发展,降低岩石的强度,同时对软化区裂纹的扩展、贯通起到加剧作用。通过微观数字图像试验分析发现,高围压条件下大理岩断口裂纹长度小、密度大、分布相对均匀,给出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机理提供了可靠的试验依据。

In order to probe the effects of high confining pressure and high hydraulic pressure on the marble characters of strength, deformation, brittle-ductile transition and rupture, and damage degradation, the triaxial compression contrastive tests of marble specimens, which are collected from surrounding rocks of diversion tunnel in Jinping hydroppwer station Grade II, are tested respectively under three different states of high hydraulic pressure, and high and low confining pressure. Then the microtest (SEM) is 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 high confining pressure. The existing of high hydraulic pressure constrains the development of brittle-ductile transition, reducing the strength and intensifying fission cracking in soften area. Based on the testing analysis of microcosmic digital image, there are smaller fissions, higher density and even distribution under high confining pressure than under low one. Microcosmic damage mechanics of rock cracking under high confining pressure and hydraulic pressure is given. Reliable testing basis is offered to analyze further failure and stability of the noncircular cave surrounding rock under high confining pressure and high hydraulic pressure.