Three dimensional numerical analysis of the effects of tunnelling near piled structures

The construction of tunnels in soft ground leads to ground movements. In urban areas with soft soils, these movements can affect the safety of surface structures. This paper investigates the interaction between tunnelling in soft soil and adjacent piled structure. Several three-dimensional finite element analyses are performed to study the deformation of pile caps and piles during the construction of a nearby tunnel. Comparison between free field and coupled analyses is also presented. To simulate the tunnelling process and its effects on piled structures, one symmetric half of the soil medium, the tunnel boring machine, the face pressure, the final tunnel lining, the pile caps, and the piles are modelled in several construction phases. The first part of the paper describes the adopted numerical model. Then, pile cap movements as well as pile deformation and bending moments resulting from the tunnelling process are investigated. The influence of the superstructure stiffness and its gravity load level on the tunnelling-produced response of the pile foundation is also investigated. Finally, the results of coupled analyses, which include the superstructure, are compared to those obtained using the analysis of piles alone (excluding the superstructure). This comparison helps to evaluate the later type of analysis that is typically implemented in routine designs.