Back analysis for tunnelling induced ground movements and stress redistribution

Analysing tunnelling process in 2D plane strain conditions is widely used method to calculate tunnelling induced settlement profiles as well as soil structure interactions. Possibility of damage to the surface and/or underground structures can be estimated using powerful finite difference method (FDM) and finite element method (FEM) of analysis. However, setting up a realistic model that would be able to achieve this goal is rather difficult. In this paper, 2D FDM analysis has been conducted to assess tunnelling induced settlement, stress redistribution phenomena along with movements around shallow soft ground tunnels excavated in accordance with the New Austrian Tunnelling Method. Measurements recorded during construction of the Heathrow Express Trial Tunnel in London Clay were compared with the predicted values to validate numerical estimations. As a soil model, the Mohr-Coulomb plasticity model has been used in the FDM analysis. Results obtained from 2D FEM are also included in this paper for comparison purposes to evaluate performance of both numerical analysis procedures. Predictions from both FDM and FEM analyses proved to be procedures used within this work can be a tool in practical engineering applications to simulate tunnelling operations. (c) 2005 Elsevier Ltd. All rights reserved.