基于一种脆性指标确定岩石残余强度

Determination of residual strength of rocks by a brittle index

岩石的残余强度是岩石力学的重要指标,准确地评价岩石残余强度对于评价地下工程的稳定性以及优化岩体支护设计具有重要意义。基于岩石的三轴力学特性提出一种表征岩石峰后强度衰减行为的力学指标——岩石强度衰减系数,该指标可反映岩石的脆性程度,并提出岩石强度衰减系数与围压关系的幂函数模型。对22组不同成因的岩石常规三轴压缩试验数据进行幂函数模型参数拟合,发现不同岩石拟合所得参数离散性较大,分析其原因主要与岩石矿物组成和岩石结构特征等因素相关。在此基础上提出基于强度衰减方法确定岩石残余强度的方法,分析表明,该方法能够很好地拟合岩石残余强度试验数据,并能反映岩石结构性质对残余强度的影响。

Residual strength of rocks is an important parameter in rock mechanics, because it has a significant influence on accurately evaluating stability of underground excavations and optimizing design of rock mass support. Based on triaxial mechanical properties of the rock, an index, defined as the strength degradation coefficient, is proposed to describe the post-peak strength degradation of rock. In this paper, the index is in essence a brittle index for rocks. A power model is then proposed for the relationship between the strength degradation coefficient and the confinement stress. By fitting the data from 22 lab triaxial compression tests, it is found that the parameters in the model which are different in various rocks can be mainly related to the mineralogical composition and the structure of rocks. Furthermore, a strength degradation method based model is proposed for determining the residual strength of rocks. It is found that the proposed model fits triaxial compression test data of rocks better than the classical Mohr-Coulomb failure criterion does. Meanwhile, it can reflect the influence of structural properties on the residual strength of rocks.