2-D and 3-D finite element analyses for the settlement due to soft ground tunnelling

Abstract

The objective of this paper is to describe and evaluate two-dimensional and three-dimensional Finite Element analyses for New Austrian Tunnelling Method (NATM) in soft ground. Firstly, 2-D plane strain FE analyses were conducted to predict ground response to NATM tunnelling. In order to take account the deformations prior to lining installation Hypothetical Modulus of Elasticity (HME) soft lining approach were adopted. The best 2-D model whose predictions were in a great agreement with the field measurements was found to be sequential excavation model (SEM), which follows closely the construction sequences used in the field. Secondly, three-dimensional FEM analysis has been carried out to predict transverse and longitudinal settlement profiles. Results from the analyses compared with each other as well as field measurements recorded during construction of Heathrow Express Trial tunnel in London clay.