Centrifuge modelling of tunnel-pile interaction

Abstract

The behavior of piled foundations due to tunneling-induced ground deformations is currently not well understood and few case studies exist in the literature. A centrifuge model study is hence carried out to investigate the effects of tunnel excavation on adjacent piles in sand. A technique proposed by Sharma et al. (2001) for the simulation of tunnel excavation in the centrifuge has been adopted in the present study. The first part of the study focused on the pile responses due to adjacent tunneling with moderate tunnel volume loss of 3.5% in dry sand. The maximum induced bending moment and axial load on the pile are observed to be located around the depth of tunnel center. The second part of the study focused on the pile responses due to tunnel excavation with very large volume loss. As expected, the induced pile head deflection, maximum bending moment and axial load due to tunneling are much larger than those under moderate volume loss.In the third part of the study, parametric studies involving distance between the pile and the tunnel and tunnel volume loss are performed. For cases with the same tunnel volume loss, the results reveal that the maximum induced pile bending moment and axial load decrease exponentially with increasing distance between the pile and the tunnel. For piles located at the same distance from the tunnel vertical center-line, the maximum induced bending moment and axial load on the pile increase logarithmically with tunnel volume loss. In the fourth part of the study, the performance of long piles and short piles are investigated. It is found that the elevation of maximum bending moment of a short pile is higher than that of a long pile. The axial load distribution of a short pile differs greatly from that of a long pile. The pile head restraint is investigated in the fifth part of the study. With the same distance from the tunnel vertical center-line and volume loss, the pilea??s fixed-head bending moment and axial load differ greatly from those of a free-head pile. Significant shear force at the pile head and large negative bending moment around the upper part of the pile are caused by the pile head restraint.