3D modeling of tunnel excavation using pressurized tunnel boring machine in overconsolidated soils

The construction of shallow tunnels in urban areas requires a prior assessment of their effects on the existing structures. In the case of shield tunnel boring machines (TBM), the various construction stages carried out constitute a highly three-dimensional problem of soil/structure interaction nd are not easy to represent in a complete numerical simulation. Consequently, the tunnelling-induced soil movements are quite difficult to evaluate. A 3D simulation procedure, using a finite ifferences code, namely FLAC3D, taking into account, in an explicit manner, the main sources of ovements in the soil mass is proposed in this paper. It is illustrated by the particular case of Toulouse ubway Line B for which experimental data are available and where the soil is saturated and ighly overconsolidated. A comparison made between the numerical simulation results and the insitu easurements shows that the 3D procedure of simulation proposed is relevant, in particular regarding he adopted representation of the different operations performed by the tunnel boring machine excavation, confining pressure, shield advancement, installation of the tunnel lining, grouting f the annular void, etc). Furthermore, a parametric study enabled a better understanding of the singular ehaviour origin observed on the ground surface and within the solid soil mass, till now not entioned in the literature.