节理峰值抗剪强度试验研究

EXPERIMENTAL STUDY OF PEAK SHEAR STRENGTH OF ROCK JOINTS

节理的三维形貌特征是影响节理剪切力学行为的重要因素。为了深入研究三维形貌特征对岩石节理峰值抗剪强度的影响,制备花岗岩和红砂岩人工劈裂岩石节理试样,并在常法向应力条件下进行了2种岩样节理的直剪试验,法向应力变化范围为0.325~8.000 MPa。在直剪试验前对节理表面形貌进行测量,并计算其三维形貌参数最大接触面积比A0、最大有效剪切倾角θ*max和粗糙度参数C。通过对三维形貌参数和直剪试验结果的分析,基于三维形貌参数最大有效剪切倾角θ*max和粗糙度参数C,建立节理峰值抗剪强度模型。最后,引用Grasselli的30组直剪试验数据对模型进行验证计算,并结合本文的20组试验数据,与Grasselli和夏才初的节理强度模型进行对比分析,结果表明新模型有合理的改进,而且能够很好地预测节理的峰值抗剪强度。

The three-dimensional morphology(3D) of a rock joint has a great impact on its shear behavior. In order to study the relationship between the characteristics of three-dimensional morphology and the peak shear strength of rock joints,the rock samples with fresh tensile joint of granite and sandstone were prepared and the direct shear tests were carried out under different constant normal stresses. The morphology of each joint was measured before the direct shear tests. The three-dimensional morphological parameters of each joint were calculated. Then,by analyzing the test results, a new peak shear strength criterion for rock joints was proposed using two three-dimensional morphological parameters which were termed as the maximum apparent dip angle θ*max and a roughness parameter C. Direct shear test data of tensile rock joints collected from Grasselli′s research were used to further verify the proposed criterion. A comparison among the new criterion,Grasselli′s criterion and Xia's criterion was made regarding the rationality of the formula and the prediction accuracy with 50 groups of joints. It was shown that the new criterion had some advantages in predicting the peak shear strength for rock joints.