Tunnel inflow monitoring in permeable rocks nearby Cannero River, Piedmont (Northern Italy)

Analytical methods used in engineering practice for a preliminary tunneling design do not adequately account for the domain limitation due to a river. In order to forecast the flow rate that has to be extracted to reach a sustainable water head in tunnel, the design must consider the changes of river hydrometric level and their consequences on piezometric head. The river is taken in account and the constraints of analytical solutions are discussed assuming isotropic and infinite domain. In particular, the study develops a formulation considering the variation of hydrograph in the river and different location of tunnel in the aquifer nearby the stream. Then, this equation was applied to a preliminary tunneling design in Cannero Valley., Northern Italy (Piedmont). The results, compared with analytical model's ones show that the analytical approach leads to a good estimation of the tunnel inflow and, the analytical to a preliminary evaluation of its most suitable location.