The Impact of micro-tunnelling on adjacent pile foundations

Abstract

A series of finite element simulations via PLAXIS were carried out to investigate the effects of micro- tunnelling on nearby pile foundations. A numerical model concerning the large diameter tunnel boring machine was first established based on identical properties of the centrifuge experiment executed by Loganathan et al. (2000). Results from numerical simulation were validated by measured data from the centrifuge test. After the validation of the numerical modelling method, the model was adjusted to match the case of micro-tunnel and a new model regarding the micro-tunnelling procedure was generated based on geotechnical conditions of the North/South Metro Line Amsterdam. The Hardening Soil constitutive model was chosen for all soil layers. In the model, the condition of single bored pile with working load was activated in the greenfield condition before the simulation of micro- tunnel. Advancement procedure of the micro-tunnel was simulated, and pile responses were collected under the plane strain condition. Based on the study of the model, two load transfer mechanisms of piles during tunnel-pile interaction process were identified. Impact of tunnel advancement on adjacent piles was also interpreted. A set of parametric studies were implemented to study changes of pile settlement and bearing capacity with increasing volume loss. An influence zone around the micro- tunnel respecting the potential of pile critical movements was established. Although the lack of field data makes the validation of results hard, comparison with analytical prediction and measured data from the centrifuge test shows good agreements for soil movements and pile responses. The results of this research remain to be validated by field data but it can provide insights into the problem of the impact of micro-tunnelling on piles.