TBM soft ground interaction: Experimental study on a 1 g reduced-scale EPBS model

This paper brings new elements of understanding on the stress-strain behaviour of soils during tunnel excavation using earth pressure balance shields (EPBS), thanks to laboratory tests carried out with an original reduced-scale physical model. Typical experiment results obtained during tunnelling with different soil types (purely frictional, cohesive-frictional) and different geometries (homogeneous or stratified grounds) are presented and discussed. These results mainly concern the soil stress-strain behaviour around the tunnel boring machine (TBM) and the soil-machine interaction at ideal rates of excavation. Firstly, results concerning the identification of pertinent control parameters to guarantee the safe advancement of the machine and the ground-supporting function of the cutting wheel are analysed. Surface settlements, stresses and displacements around the tunnel and behind the tunnel face, as well as arching effects around the shield are then presented and discussed.