岩石变形劣化全过程细观试验与细观损伤力学模型研究

 采用细观试验探究岩石变形劣化全过程是了解岩石变形破坏机制的重要手段。选取四川锦屏二级水电站深埋(2 525 m)隧洞围岩(大理岩)，利用岩石变形破坏全过程细观力学试验系统，进行大理岩试样单轴压缩变形破坏全程的数字化试验，在SEM图像数字化处理基础上，对微裂隙的萌生、扩展及贯通过程进行数字化定量分析，统计试样在受压过程中微裂纹的面积、方位角、长度、宽度和周长基本几何数据。利用内变量热力学理论和摩擦弯折裂纹模型，分析微裂纹不同阶段的演化规律，建立微裂纹引起的非弹性应变与应力之间的定量关系，得到大理岩应力–应变关系计算曲线，并与试验结果对比，验证了本文理论模型的可靠性，从试验和理论两方面探究岩石试样单轴压缩过程中的破坏机制。

MESOSCOPIC EXPERIMENT ON DEGRADATION EVOLUTION OF ROCK DEFORMATION AND ITS MESO-DAMAGE MECHANICAL MODEL

Investigating the degradation evolution process of rock deformation by mesoscopic experiment is an important means to understand its deformation and failure mechanisms. In this paper，the marble samples are taken from the tunnels of Jinping II hydropower station with an overburden depth of 2 525 m. By mesomechanical test system，axial compression test is carried out to record the whole degradation deformation process of rock. With the image processing technique of scanning electron microscope(SEM)，we quantitatively analyze the initiation，propagation and coalescence processes of microcracks；and the data of microcracks′ area，azimuth angle，length，width and perimeter are obtained. Meanwhile，internal variable thermodynamics theory and frictional kinking crack model are employed to understand the evolution process of microcracks at different stages. Quantitative relationship between nonelastic strain(induced by microcracks) and stress is established and theoretical curve of stress vs. strain is also derived. With the experimental results，validity of the theoretical model is verified，and the failure mechanism of rock samples under axial compression is investigated in terms of experiment and theory.