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.