In spite of an evident role of operational procedures on the mechanisms induced by tunnelling, technological aspects are poorly taken into account when performing design analyses. Important factors such as face-support load or grouting of the lining extrados in mechanized tunnelling are chosen with a mix of sound theoretical rules and empirism, and the risk of introducing subjective assumptions is high. The present work explores the possibility of using advanced numerical modelling to optimize these choices with regard to the possible negative consequences on the surrounding environment. With this aim, a three dimensional FEM model has been built reproducing in the most realistic way the excavation process followed for an EPB shield driven tunnel in Bangkok. The subsoil stratification, the initial hydrodynamic conditions and the pore pressures transient variation induced by the tunnelling operations are modelled with non-linear coupled soil models. The excavation sequence is carefully reproduced taking into account the support pressure applied on the front face, the advance of a conical shape shield, the placing of lining segments, the filling of tail voids with grout having time dependent behaviour and the weight of the backup trailer. The model is successfully validated comparing computed and recorded ground settlement profile and its capability is finally evaluated looking at the ground deformations and convergence induced by a parametric variation of the tail void injection and of the face pressure.

Effects of mechanized tunnelling studied with numerical models

MODONI, Giuseppe;
2016-01-01

Abstract

In spite of an evident role of operational procedures on the mechanisms induced by tunnelling, technological aspects are poorly taken into account when performing design analyses. Important factors such as face-support load or grouting of the lining extrados in mechanized tunnelling are chosen with a mix of sound theoretical rules and empirism, and the risk of introducing subjective assumptions is high. The present work explores the possibility of using advanced numerical modelling to optimize these choices with regard to the possible negative consequences on the surrounding environment. With this aim, a three dimensional FEM model has been built reproducing in the most realistic way the excavation process followed for an EPB shield driven tunnel in Bangkok. The subsoil stratification, the initial hydrodynamic conditions and the pore pressures transient variation induced by the tunnelling operations are modelled with non-linear coupled soil models. The excavation sequence is carefully reproduced taking into account the support pressure applied on the front face, the advance of a conical shape shield, the placing of lining segments, the filling of tail voids with grout having time dependent behaviour and the weight of the backup trailer. The model is successfully validated comparing computed and recorded ground settlement profile and its capability is finally evaluated looking at the ground deformations and convergence induced by a parametric variation of the tail void injection and of the face pressure.
2016
978-80-906452-0-2
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11580/59229
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