渗流状态下非规则砂岩节理峰值剪切强度经验公式

An empirical formula for peak shear strength of irregular sandstone joints under seepage flow

为研究渗流条件下岩石节理的剪切力学特性,采用基于RDS-200型岩石直剪仪改造的剪切-渗流试验装置,分别进行了10组无渗流自然状态下和25组渗流状态下的非规则砂岩节理直剪试验,分析渗透水压、法向应力和节理粗糙度等因素对岩石节理剪切力学特性的影响,并提出渗流状态下非规则砂岩节理峰值剪切强度经验公式。研究结果表明,与无渗流自然状态相比,岩石节理在渗流作用下整体呈现峰值剪切强度减小,峰值剪切位移增大和峰前剪切刚度减小的特征。基于Barton提出的岩石节理峰值剪切强度经验公式,结合有效应力原理,并考虑渗透水压对基本摩擦角的影响,提出渗流条件下非规则砂岩节理峰值剪切强度经验公式。该公式仅增加了2个易于获取的试验参数(岩石节理壁强度JCS和渗透水压),对渗流条件下砂岩节理剪切强度试验数据拟合效果较好,对于准确估计渗流条件下岩石节理峰值剪切强度具有一定帮助。

To study the effect of seepage on shear mechanical properties of rock joints,direct shear tests on 10 irregular sandstone joints in non-seepage natural state and 25 irregular sandstone joints in seepage state were carried out using the rock joint shear-seepage test device which is modified by RDS-200 rock direct shear apparatus.The influences of seepage pressure,normal stress and joint roughness on the shear mechanical properties of rock joints are analyzed,and the empirical formula for the peak shear strength of irregular sandstone joints under seepage is proposed.The results show that compared with the natural state without seepage,the peak shear strength of rock joints decreases,the peak shear displacement increases,and the pre-peak shear stiffness decreases in seepage state.Based on the empirical formula of peak shear strength of rock joints proposed by Barton,considering the effective stress principle and the influence of seepage water pressure on the basic friction angle together,the empirical formula of peak shear strength of irregular sandstone joints under seepage condition is proposed.Only two test parameters which can be easily to obtain(rock joint wall strength JCS and seepage water pressure)are added in the formula,and it has a good fitting effect on the test data of rock joint shear strength under seepage condition,which is helpful to accurately estimate the peak shear strength of rock joint under seepage condition.