Anti-seismic effect analysis of two kinds of surrounding rock grouting measures in the shallow and eccentric pressure section of tunnel portal

In order to further improve the safety of the shallow overburden and eccentric pressure section of the tunnel portal during earthquake, based on a railway tunnel portal section project, the seismic effect of two kinds of surrounding rock grouting anti-seismic measures were studied by using the finite difference numerical calculation software, and the influence of two kinds of anti-seismic measures of contact grouting and interval grouting on the displacement and internal force of the tunnel lining structure is compared and analyzed. After the contact grouting is adopted in the surrounding rock, the results show that the lateral and longitudinal displacements of the secondary lining structure are reduced by 86.7% and 38.1% respectively, the axial force and bending moment are reduced by 45.12% and 64.20% on average, and the minimum safety factor is increased by 61.36% on average; after interval grouting, the lateral and longitudinal displacements of the secondary lining structure are reduced by 49.3% and 23.8% respectively, the axial force and bending moment are reduced by 39.42% and 44.90% on average, and the minimum safety factor is increased by 43.11% on average. The anti-seismic effect of contact grouting is better than that of interval grouting. The research results can provide reference for the development of anti-seismic technology of tunnel portal section.