Development of a 3D finite element model for shield EPB tunnelling

Abstract

The paper describes the main features and presents the results of a 3D finite element model for shield EPB tunnelling based on the FE code Simulia ABAQUS. The model simulates important components of the mechanised excavation process including variable muck pressure on the excavation face, cutterhead overcut, shield conicity, installation of jointed segmental lining, annular gap grouting and time-dependent setting of the grout. Advanced numerical techniques are used to model the shield - ground interface, time dependent grout setting and the configuration and stiffness of the segmental lining joints. Three lining models are investigated and compared: continuous shell without joints, shell with aligned joints (2D joint configuration) and shell with staggered (rotated) joints, which is the most realistic 3D lining model.The results of the numerical analyses highlight the importance of modelling the above features on ground deformations and internal forces of the lining. It is shown that: (1) even moderate face pressure can appreciably reduce ground loss and prevent potential face instability in very weak ground, (2) cutterhead overcut and shield conicity have a pronounced effect of ground surface settlement which can be partly compensated by increasing the grout pressure during tail grouting and (3) a continuous shell model is a reasonable approximation of segmental lining for shallow tunnels.