A comparison of 2D and 3D numerical simulations of tunnelling in soft soils

Tunnel excavation is a three-dimensional problem, especially in the zone close to the tunnel face. However, despite recent advances in computing resources, a full 3D numerical analysis is usually complex and requires important computational resources (both in terms of storage and of time). Two-dimensional simulations are therefore often used. In this paper, the Hanoi metro system is used as a case study. A numerical investigation is performed to evaluate the applicability of 2D deconfinement methods. These methods consider pre-displacements of the soil surrounding the tunnel before installation of the tunnel structure to model the 3D phenomenon which occurs at the tunnel face. The obtained results allow estimating the 2D deconfinement method which gives the better agreement with the 3D model in terms of both soil movements and structural forces induced in the tunnel lining using an error function. These estimations were performed at different sections along the tunnel direction in order to highlight the effect of the tunnel advancement on the applicability of 2D deconfinement methods.