Abstract: As the key technical means of surrounding rock stress control,the layout of advanced pilot tunnel is of great significance to ensure the stability of the project.In order to further reveal its mechanism of action,the finite difference method and particle flow numerical simulation software were used to systematically study the macroscopic mechanical response and mi croscopic failure mechanism of rock during the excavation of the advanced pilot tunnel of deep buried tunnel.The results show that the stress state of surrounding rock changes from three-way compression to two-way compression during the excavation of the advanced pilot tunnel of deep buried tunnel.As the dip angle of the pilot tunnel increases,the rock strength decreases first and then increases.The optimal pressure relief effect can be achieved by using the 45° dip angle pilot tunnel arrangement.Un der biaxial compression,the rock with holes is dominated by tensile cracks,and the proportion of tensile cracks under the load ing-unloading path is higher than that under the pure loading path.The influence of intermediate principal stress on rock me chanical properties under pure loading path is significantly higher than that under loading-unloading path,and there is a stron ger positive correlation between octahedral shear stress and average stress.The research results can provide theoretical basis and technical support for the stability control of surrounding rock in deep tunnel engineering.

Key words: advance pilot tunnel,stress path,intermediate principal stress effect,deep buried tunnel