隧道破裂围岩抗剪力学性能分布规律研究

Study on Distribution of Shear Mechanical Properties of Fractured Surrounding Rock Masses Within Tunnel

摘要:

为探究隧道破裂围岩剪切力学性能随距离隧道边墙不同深度的变化规律,采用现场测试与数值模拟相结合的方法开展研究。首先,基于窗口法建立了隧道围岩表面裂隙网络模型;然后,采用钻孔摄像获取距离隧道边墙不同深度位置的裂隙分布图像,对不同深度位置的裂隙网络参数进行优化,将围岩由表面到内部分为5个区域,得到了破裂围岩从表面到内部的裂隙网络优势组的直径和体密度变化规律;随后,采用离散元数值软件PFC3D建立不同区域破裂岩体模型,开展直剪试验获得剪切力学参数,结果表明黏聚力随着深度的增加逐渐增大,与6~8 m深度相比,8~10 m深度黏聚力呈继续增大趋势,而内摩擦角开始趋于稳定,且随着深度的增加而略微减小,采用双孔声波测试法对围岩剪切力学性能参数分布规律进行了验证;最后,基于直剪试验中对不同深度处岩体剪切力学参数的研究,采用数值模拟方法构建不同围岩区域数量的隧道模型,将围岩按深度划分成代表不同剪切力学参数的区域,并对赋予不同力学参数下的隧道变形情况与现场监测结果进行对比分析,结果表明,划分更多区域的隧道模型的拱顶沉降值与拱脚水平收敛值更符合现场实际情况。

Abstract:

To investigate the variation in shear mechanical properties of fractured surrounding rock at different depths from the tunnel sidewall, combining field tests and numerical simulations. First, a surface fracture network model of the surrounding rock was established using the window method. Then, drilling cameras were used to obtain images of crack distribution at different depths from the tunnel sidewall, and the crack network parameters at different depth positions were optimized. The surrounding rock was divided into 5 regions from the surface to the interior, and the diameter and bulk density variation patterns of the dominant fracture network from the surface to the interior of the fractured surrounding rock were obtained; Subsequently, discrete element numerical calculation software was used to establish models of fractured rock masses in different regions, and direct shear tests were conducted to obtain shear mechanical parameters. The results showed that both cohesion and internal friction angle of the rock mass generally increase with depth. Compared with the 6 to 8 m region, the cohesion in the 8 to 10 m region continued to increase, while the internal friction began to stabilize and slightly decreased with depth. And verify the distribution law of shear mechanical performance parameters of surrounding rock through dual hole acoustic wave testing method; Finally, based on the study of shear mechanical para-meters of rock mass at different depths in direct shear tests, numerical simulation methods were used to construct tunnel models with different numbers of surrounding rock areas. The surrounding rock was divided into regions representing different shear mechanical parameters according to depth, and the deformation of the tunnel under different mechanical parameters was compared and analyzed with the on-site monitoring results. The results showed that the settlement value of the arch crown and the horizontal convergence value of the arch foot of tunnel model, which divided more regions, were more in line with the actual situation on site.