Soil-tunnel Interaction Model Considering Cross-sectional Flattening and Warping

Abstract:

The paper regards the tunnel as a thin-walled ring structure with four deformation modes， including bending， shearing， warping and flattening， on elastic foundation， by introducing the Generalized Beam Theory and three-dimensional soil reactions. The finite element solution of the proposed soil-tunnel model considering coupled transverse and longitudinal actions is derived. The effectiveness of the model is verified by two case studies. Furthermore， the effects of tunnel width-to-thickness ratio and soil resistance coefficient on the transverse and longitudinal behaviours of the tunnels are obtained by parametric analysis. The results show that： The effect of warping and flattening on tunnel with large diameter are significant under high-stress external load， where the cross-section presents a typical form of "horizontal duck egg" and the warping aggravates the longitudinal strain of the tunnel with more than 30% increasing. The smaller the thickness to diameter ratio of tunnel is， the larger the transverse and longitudinal deformation are. The increasing amplification can reach about 30%. The longitudinal behaviors of the tunnel are more sensitive to tangential soil resistance coefficient than the normal coefficient， while the cross-sectional performance is equally sensitive to bidirectional soil resistance coefficient.