3D finite element investigation on Influence of the lagging distance between side-by-side twin tunneling on existing pile

Abstract

Nowadays, there is a growing number of underground transportation systems in congested urban areas, especially for twin tunnels. Consequently, these tunnels are unavoidably constructed adjacent to the existing structures (e.g., piled foundations). According to a large number of previous studies, they indicated that the new tunnel construction can cause excessive ground movement and this movement can lead to a damage on existing nearby piles. Therefore, the impact of twin tunneling on the existing piles should comprehensively be investigated. However, various studies have been considered only the influence of relative position between tunnel and pile but the important effect of lagged distances between the twin tunnel faces on ground movement has never been concerned. In this study, a three-dimensional numerical analysis is performed to investigate the influence of side-by-side twin tunneling on the behaviors of the existing single pile. The finite element procedure and soil parameters are calibrated against well-documented tunneling case history of Bangkok MRTA blue line project. To understand the influence of lagging distance between twin tunnel faces on the behaviors of existing pile, five different lagging distances (i.e., 0Ls, 1Ls, 3Ls, 5Ls, and 8Ls when Ls is shield length) are carried out as the case studies. Numerical results indicate that the lagging distance between twin tunnel faces significantly affects not only on the ground movement but also on the behaviors of the existing pile.