3D numerical simulation of TBM excavation for predicting surface settlements - state of the art

Tunnels offer efficient transportation infrastructure in urban areas such as the Grand Paris Express in France. In urban areas, a densely built environment is exposed to the surface settlements caused by tunneling, and consequently, vulnerable buildings and infrastructure can be damaged. To mitigate this risk, the tunneling process is designed such that the surface settlements remain below a given threshold. Many numerical methods have been developed and are commonly used to simulate the surface settlements induced by a tunnel boring machine (TBM). In this paper, the first objective is to present the state of the art of TBM excavation 3D finite element (FE) modeling. From this literature review, each modeling approach is compared with respect to defining the geometry, meshing, setting the boundary conditions, and implementing TBM excavation parameters. Also, many simulations must be run to validate the modeling assumptions, calibrate the model using sensor data, and account for uncertainties in the boundary conditions, soil properties, and tunneling process. The second objective of this review of the literature thus is to identify the driving instruction parameters that impact settlements and methods to implement them in a 3D finite element model.