砂岩试件加载-卸荷-加载损伤弱化试验分析

为研究深部巷道围岩开挖和回采全过程中岩体强度的弱化规律,通过对砂岩试件进行不同加载速率的单轴加载、不同围压的三轴加载以及不同程度的三轴加载-卸荷-单轴加载试验对砂岩试件在加载、卸荷和再加载过程中的损伤、弱化机理进行研究。结果表明:试件的峰值强度与加载速率之间呈幂函数关系,与围压之间呈线性关系,加载速率和围压越大,砂岩试件强度越高。砂岩在三轴加载-卸荷-单轴加载时试件最终破坏形态与其受载历史无关,与岩石的最终受力状态相关。岩石的最终强度与其受载速率、围压大小和加卸-载扰动等受载历史相关,初始轴压越大加载速率越小试件的初始损伤越大,卸载后再加载的最终强度越小。此外,提出了基于能量密度的岩石损伤度指标和一种基于加载过程状态的强度弱化计算方法,经计算验证该方法是可行的。

Test and analysis of sandstone damage-weakening under loading-unloading-loading

In order to investigate the weakening law of rock mass mechanical properties in the whole process of deep roadway surrounding rock excavation,the sandstone specimen tests of uniaxial loading with different loading rates,triaxial loading with different confining pressures and triaxial loading-unloading-uniaxial loading with different degrees are carried out to study the damage and the weakening mechanism in the process of loading,unloading and loading.The results show that there is a power function between the peak strength and the loading rate,and a linear relationship with the confining pressure.The higher the loading rate and confining pressure are,the higher the strength of sandstone specimens is.The ultimate failure mode of sandstone in the triaxial loading-unloading-uniaxial loading is not related to the loading history,but is related to the ultimate stress state of rock.The ultimate strength of rock is bound up with the loading rate,confining pressure and loading and unloading disturbance of loading history.The larger the initial axial pressure and the initial damage are,the smaller the ultimate strength of the unloading and loading is.In addition,the rock damage index based on the energy density and the strength weakening calculation method based on the state of the loading process are put forward,which is proved to be feasible by the calculation.