Tunneling Effects on Pile Group Response in Bangkok

Abstract

Tunneling adjacent to an existing pile group may induce additional force, bending moment and settlement of a pile. Moreover, it may cause load redistribution and differential settlement in a pile group. In this paper, the construction of a water diversion tunnel with an outside diameter (D) of 5.55 m constructed in Bangkok is reported. The tunnel was constructed in very stiff clay using an earth pressure balance shield with a cover-to-diameter ratio of 4.5 and very close to a pile group. The pile group was located within a distance of 1D from the tunnel springline. Tunneling induced ground responses were measured by using surface settlement points, extensometers and inclinometers. To investigate the influence of tunnelling on the pile group, a three-dimensional, elasto-plastic, coupled-consolidation numerical analysis was also conducted to simulate the pile group responses. Observed ground responses and computed changes of horizontal effective stress and excess pore water pressure around piles are reported. Redistribution of pile shaft resistance, load transfer in the pile group and pile head settlements are investigated.