Study on the influence factors of soil arch morphology and mechanical properties of lining structure in high-filled cut-and-cover tunnels postprint

Abstract: The load reduction mechanism of high-filled cut-and-cover tunnels is reducing the earth pressure above the tunnel by increasing the settlement difference inside the backfill soil, so as to reduce the stress of the lining structure. The load reduction effect of high-filled cut-and-cover tunnels depends on the strength of soil arch effect. However, the relationship between the strength of soil arch effect and soil arch morphology is not clear. In order to optimize the design of lining structure and improve the safety of lining structure, it is necessary to clarify the influences of soil arch morphology on soil arch effect. Therefore, based on the finite difference software FLAC3D, with the groove and tunnels width ratio and slope angle as variables, the earth pressure of backfill, the soil arch morphology of backfill and the stress of lining structure of high-filled open-cut tunnel with EPS plate and concrete column load reduction are studied. The influences of groove and tunnels width ratio and slope angle on the earth pressure of high-filled open-cut tunnel and the stress of lining structure are analyzed from the perspective of soil arch morphology. The results show that the vault and inverted arch of the tunnel are subjected to compression, and the lateral side of the side wall is subjected to tension, and the boundary point of tension and compression outside the tunnel appears at the arch waist. Reducing the groove and tunnel width ratio or increasing the slope angle will make the soil arch effect more obvious, the load reduction effect is better, the stress of the lining structure is smaller, and the lining structure is safer. The strength of soil arching effect is determined by the thickness of soil arch and the area of soil arch area above the open. The larger the thickness of soil arch is, the larger the area of soil arch area above the open tunnel is, and the better the load reduction effect is, which is independent of the position of soil arch and the total area of soil arch area. In practical engineering, the structural stress should be optimized by controlling the thickness of soil arch and the area of soil arch area above the open hole.