Numerical simulations of tunnelling in soft rock under water pressure

The paper deals with the effect of the groundwater nd time on the behaviour of tunnels in soft rocks. Herewith, a short review illustrates the basic prin ciples governing the influence of the pore pressure on the soft rocks behaviour and u nderground excavation performance. Then, the main ways for the tunnel equ ilibri m analysis are presented and discussed by assuming short and long term conditions. This type of analysis allows a first estimation of the tunnel be haviour, but, in many cases, a more exhaustive simulation is required in order to optimise the tunnel analysis and design. Thus, a 3D simulation of a mechanised tunnelling in soft rock under water pressure is finally exposed. This kind of analysis allows shedding light on the effects of the advancement rate, the permeability, the previous drainage of the soil and other effects on the displacements and stresses along the tunnel. The paper also describes the main parameters requir ed to continuously ensure the transient equilibrium during tunnel excavation, con tr lling both processes simultaneously: mechanical and fluid calculations.