损伤石灰岩单轴再加载力学特性及破坏机理

为研究卸荷损伤破坏围岩力学特性及破坏机理,选用RMT-150岩石力学试验系统进行三轴岩石加载-卸载过程,制备损伤岩石。结合AEwin声发射系统开展损伤石灰岩单轴再加载试验,测试应力-时间-能量累计值关系曲线,分析阐述岩石宏观破坏特征。结果表明:随着卸荷点的增加,损伤石灰岩破坏程度与破坏形式均发生较明显的变化。石灰岩破坏形式从脆性破坏向延性破坏转化,扩容现象越来越不明显;低于70%峰值强度卸荷点的损伤岩石单轴加载过程中声发射能量累计值增长规律趋于一致,可分为平稳阶段、稳定增长阶段、二次平稳3个阶段;岩石内部微裂纹分布方式对宏观破坏特征影响明显,岩石细观力学响应决定其宏观力学破坏特征。

Mechanical properties and failure mechanism of damaged limestone under uniaxial reloading

In order to study the mechanical properties and failure mechanism of unloading damaged surrounding rock, RMT-150 rock mechanics test system was selected to carry out tests on triaxial rock in loading-unloading process to prepare damaged rock. Combined with AEwin acoustic emission system, the uniaxial reloading test was conducted on damaged limestone, the relationship curve of stress-time-energy accumulation was tested, and the macroscopic failure characteristics of the rock were analyzed. Experimental results show that with the increase of unloading points, the damage degree and failure form of the damaged limestone were changed obviously. The failure form of the limestone transformed from brittle failure to ductile failure, and the phenomenon of expansion was less and less obvious. In the process of uniaxial loading, the variation in the cumulative value of the acoustic emission energy of the damaged rock with peak strength lower than 70% tended to be the same, which can be divided into three stages: stable stage, stable growth stage, and secondary stable stage. The distribution mode of micro-cracks in rock had an obvious influence on its macro-failure characteristics, and the micro-mechanical response of rock determined its macro-mechanical failure characteristics.