Dynamic analysis of the effect of vertical clearance on an existing perpendicular crossing tunnel in soil.

Abstract

A 3D finite element modelling was carried out to analyse the dynamic response of two perpendicular crossing tunnels in sandy soil to understand the linings’ behaviour and surrounding soil. The parametric study included the analysis of three different amplitudes of harmonic sine waves across five cases of cross-tunnels. The results indicated that the most favourable case regarding surface settlement, maximum absolute dynamic bending moment, and horizontal convergence is when the second tunnel is located at a significant pillar depth below the first. The critical cases experience a settlement of 1.1% of the tunnel diameter, a dynamic bending moment of 13.7% lower than the single tunnel case and a dynamic horizontal convergence of 0.26%. Whilst considering dynamic earth pressure and axial thrust, the preferred location of the second tunnel can be below the first tunnel, irrespective of pillar depth. This investigation can provide a reference for designing and constructing cross-tunnels at different vertical spacing under dynamic loading conditions for dry sandy soil.