Tunnelling and groundwater interaction: the role of the hydrogeological monitoring

The interaction between tunnelling and groundwater is an important factor to be considered in any underground work. Groundwater can represent a major constraint for many technical decisions related to the tunnel construction and, at the same time, a fundamental valuable natural resource to be preserved quantitatively and qualitatively during and after the tunnel completion. The knowledge of the geological subsurface conditions, the hydrogeological mechanisms of groundwater infiltration and circulation, the degree of the aquifers connection with the river network as well as the chemical composition of the circulating groundwater are some of the more important topics that should be analysed in the early phase of the tunnel design. Moreover the numerical modelling of the tunnel-groundwater system requires a large amount of suitable data derived by field investigation. The hydrogeological monitoring represents a fundamental tool for the tunnel design, construction and functioning and has to be developed in a program which includes surface and subsurface data in an integrated geo-referred way. The system needs the continuous uploading of the environmental data coming form the tunnel and the surface environment in order to check the short and long-term interactions, verify the modelling hypothesis and monitor the dynamic behaviour of the whole system and the compliance with the local environmental regulations.