Study on Deformation of Surrounding Rock and Stress Characteristics of Lining in Tunnels Passing through Soil-rock Interface

Based on the engineering practice of loess tunnel crossing soil-rock interface, finite element numerical calculation method combined with the distribution law of soil-rock interface during tunnel construction was used to study the influence of spatial distribution position of soil-rock interface on surface displacement and convergence deformation characteristics in tunnel, and the mechanical characteristics and variation law of lining structure were obtained. The results show that when the soil-rock interface is located below the arch bottom, the tunnel excavation range is loess, the surface settlement and surrounding rock deformation are large, and the tension near the arch top of lining is large. When the soil-rock interface is above the top, the influence of tunnel excavation on surface settlement and surrounding rock deformation is basically unchanged. When the soil-rock interface is located near the arch shoulder, the tensile stress of the vault lining is the smallest, and the lining structure is more favorable. When the soil-rock interface is located near the vault, the compressive stress of the lining at the arch waist increases significantly, and the tensile stress at the vault is also large. At this time, the stress of the lining structure is the most unfavorable. Further, according to the total displacement characteristics of the lining structure, the angle of the locking anchor at the arch shoulder can be controlled to 15°~35°, and the angle of the locking anchor at the arch waist and the arch foot can be controlled to about 45°, which can provide a theoretical basis for tunnel design and construction.