Effect of TBM Advance in the Structural Response of Segmental Tunnel Lining

This study investigated the structural response of segmental tunnel linings to tunnel-boring machine (TBM) advance during the construction of a typical tunnel built in Mexico. Because of the thrusting of the TBM during excavation, an axial load acts along the longitudinal axis of the tunnel. This axial load decreases as the TBM advances away from the tunnel lining. However, the residual axial load continues acting on the lining, producing a coupling between rings that affects the structural response of the tunnel. In this paper, this effect is studied by means of finite-element models. A nonlinear parametric study was carried out in which the material properties, the influence of the number of rings, the residual axial load, and the position of continuous joints were examined. The numerical models were calibrated with (lab-based) experimental results obtained from the literature on a typical tunnel built in Europe. It was concluded that the residual load increases the structural capacity of the lining. Also, the study showed that the collapse mechanism was modified by the coupling between rings. Rings will fail by excessive deformations with less coupling, while with greater coupling, the collapse mechanism is caused mainly by cracking in the segments. Therefore, it is necessary to consider the effect of the TBM advance to evaluate the structural response of a segmental tunnel better. (C) 2017 American Society of Civil Engineers.