Mechanical response analysis of primary support for shallow buried loess tunnel under surface surcharge

At present, the research on the influence of surrounding soil deformation induced by tunnel construction under the action of surcharge is generally based on the situation after the tunnel has been built, and less consideration is given to the existence of surface surcharge near the planned route of the tunnel when the tunnel is not built. Therefore, based on the Luochuan tunnel under construction, this study monitors the deformation of shallowly buried loess tunnels under different surcharge conditions and analyzes the influence of varying surcharge conditions on the deformation and stress of the tunnel through numerical simulation to determine the effective range of surface surcharge. The results show that the influence of surcharge load on tunnel stability is the most significant when located at the tunnel axis, and the influence degree increases with the increase of load. The adverse effects of surcharge load mainly occur in the range of 2 times the tunnel diameter. Once the range is exceeded, the internal force of the tunnel support structure is not sensitive to the surcharge load. In engineering, the surface surcharge can be controlled within the safety displacement limit by referring to the displacement calculation results.