Influence of TBM geometry on lining loads of deep tunnels

The paper presents a numerical study aimed at investigating the influence of the geometrical design of Tunnel Boring Machines (TBMs) on the forces acting on the lining. The study was conducted using a 3D numerical model that accounts for the major features of the excavation such as front pressure, overcut, shield conicity, tail void grouting, grout hardening over time and installation of the lining. To accurately reproduce the soil-shield-lining interaction, a simple procedure was adopted to overcome the modelling inaccuracies associated with the misidentification of the excavation profile due to the development of pre-convergences ahead of the excavation front. A parametric study was conducted to evaluate the influence of the shield’s conicity and length on the lining forces. The results remark the great influence of the analysed parameters and show that the developed model can provide novel and significant insights on the interaction process.