Simplified Finite-Element Modeling of TBM Advancement: A Novel Computational Approach

Developing a numerical model of tunnel excavation using a tunnel boring machine (TBM) is a difficult task due to the complexity of the phenomena involved in the advancement of the machine through the ground. The ease of use of calculation software often masks (at least in part) the representation in the numerical simulation of the actual phenomenon. Many simulations use nodal forces to account for stress relaxation at the boundary of the excavated ground and for the interaction between the TBM, the grout, and the surrounding soil. However, calibrating these models may prove difficult. This paper proposes a simple approach called the swelling method, which aims to take into account the TBM control parameters, especially the grout injection parameters. This approach allows directly defining the final stress applied to the tunnel contour, taking into account the grout pressure. The conventional and the new approaches are implemented in the finite-element code CESAR (version 2024.0.5) and tested to simulate surface settlements and lateral soil displacements induced by tunneling using a full-scale research project called TULIP (Tunneling and Limitation of Impacts on Piles) as a background. The results show a strong agreement between the two methods, but the swelling method is easier to handle and has the potential to capture the complex interactions between the TBM and the surrounding soil. The influence of the model parameters on the width of the surface settlement trough is discussed.