A Case Study on Pile Performance Due to Tunnelling

Much attention has been paid in the past to study the potential impact of piled foundations onto existing tunnels in the vicinity. However, relatively less study has been done to investigate the performance/behaviour of existing foundation piles due to tunnelling works. This paper presents a case study of an instrumented low-rise building founded on piles at Circle Line Stage 3 (CCL3) in Singapore. The CCL 3 comprised the construction of five underground train stations connected by 5.7-km long-running twin tunnels. The building's protective strategy and monitoring results of vertical and lateral ground movement, vertical building movement and pile down drag force due to tunnelling works are presented in this paper. A comparison of the predicted values using the three-dimensional finite element method (FEM) program with the measured monitoring results is also discussed. A sensitive analysis with different soil/rock constituted models in the numerical modeling was also carried out. The monitoring results indicated that a significant down drag force was measured in the piles although the ground movement due to tunnelling was relatively small. The analysis results show that the numerical modelling based on a linear elastic soil/rock constituted model may over-estimate the movements and the forces on the pile under the effect of tunnelling works.