Abstract: Challenges such as deformation, water leakage, and collapse occur when excavating soft loess tunnels. Therefore, a micro-three-bench method is proposed for the large-section, shallow-buried Tianhengshan tunnel in water-rich loess strata. Then, numerical simulations and field monitoring are employed to validate the applicability of the micro-three-bench method. The research results demonstrate the following: (1) The micro-three-bench method effectively controls the surrounding rock deformation and support force, resulting in 34.6 mm tunnel crown settlement and 17.2 mm clearance convergence. The maximum stress of the surrounding rock is 102.5 kPa; the primary support closed ring is controlled at 11 m, and the three-bench and seven-step are controlled at 18 m. (2) The simulated primary support is slightly larger than the monitored data. These data present a similar trend, indicating the effectiveness of the micro-three-bench method for stabilizing the surrounding rocks of tunnels in soft loess tunnels.

Key words: tunnel construction, micro-three-bench method, loess strata, Midas