不同真三轴路径下岩石卸荷特性与破裂特征研究

Unloading properties and fracture characteristics of rock under different true triaxial unloading paths

岩石真三轴卸载应力路径试验能全面准确反映真实应力环境下岩石实际力学特性与破裂演化规律,对揭示巷道开挖等引起的围岩破坏本质原因具有重要的工程意义。通过真三轴伺服试验系统开展了一系列真三轴卸载应力路径试验,结合CT扫描技术,研究了不同应力路径下岩石强度、变形及破裂特征。研究发现:同时卸载σ和σ路径下岩石峰前持续时间最短,只卸载σ路径下岩石峰前持续时间最长,变形特征类似;真三轴卸载条件下岩石内部破裂特征较加载路径更加复杂,破裂面表面积更大;不同卸载路径下沿σ方向岩石内部主破裂面均呈“V”形且贯穿整个试样,但围压σ和σ发生转换后(σ<σ),岩石沿初始围压σ方向(新的σ方向)上产生了较为密集的破裂网络,说明岩石内部裂隙强烈依赖中间主应力方向,为工程中研究岩体破裂演化规律提供了重要的依据。

True triaxial unloading stress path test can fully and accurately reflect actual mechanical properties of rocks and fracture evolution under real stress environment, and has important engineering significance in revealing essential causes of destruction of surrounding rocks caused by roadway excavation. Combined with CT scanning technology, the rock strength, deformation and fracture characteristics under different stress paths were studied. The study has found that during simultaneous unloading of path σand σrock duration before rock peak is the shortest;during unloading of σrock duration before rock peak is the longest.;deformation characteristics are similar. Under true triaxial unloading conditions, internal fracture characteristics of the rock are more complicated than loading path, and the area of the fracture surface is bigger. Under different unloading paths, main internal fracture surface of the rock along the σdirection is “V” shape and runs through the entire sample. However, a switch in rock pressure σand σproduces a more dense network of fractures along the initial pressure direction(the new direction), which shows that internal cracks in the rock strongly depend on the direction of intermediate principal stress. This provides an important basis for studying the evolution law of the surrounding rock fracture in engineering.