The response of pile foundations subjected to shield tunnelling

Abstract

This paper presents a unique case history in Singapore on the study of the effects of shield tunnelling on the adjacent pile foundations. As part of the construction of the MRT North East Line contract 704, a viaduct bridge was planned in conjunction with the tunnel advancement. The bridge which consists of 2 abutments and 39 piers was constructed in parallel alignment with the new twin tunnels configuration. The piers were supported by groups of four to six 1.2 m diameter bored piles. Along the alignment, 6.5 m diameter tunnels were located very closely, i.e. 1.6 m clear distance, to the pile foundation. As part of the monitoring requirement, an instrumentation programme was implemented at six piers. A total of twelve piles were installed with strain gauges at various levels of foundations to monitor the piles'response during tunnelling. The data was then linked to settlement markers installed in the vicinity of the piles. The results show that the piles were subjected to large dragload particularly when higher volume loss was observed. Bending moments developed in piles were found to be much higher in the transverse direction (bending perpendicular) than in the longitudinal direction (bending parallel to tunnel alignment). © 2006 Taylor & Francis Group.