Long-term simulations of thermal and hydraulic characteristics in a mountain massif: The Mont Blanc case study, French and Italian Alps

The use of hydrothermal simulation models to improve the prediction of wate r inflows in underground works during drilling is tested in the Mont Blanc tunnel, French and Italian Alps. The negative thermal anomaly that was obse rved during the drilling of this tunnel in 1960 is reproduced by long-term, transient hydrothermal simulations. Sensitivity analysis shows the great i nertia of thermal phenomena at the massif scale. At the time of tunnel dril ling, the massif had not reached thermal equilibrium. Therefore, a set of s imulation scenarios, beginning at the end of the last glacial period, was d esigned to explain the anomaly encountered in the tunnel in 1960. The conti nuous cooling of alpine massifs due to infiltration of waters from the surf ace has occurred for 12,000 years and is expected to continue for about 100 ,000 years. Comparisons of water-discharge rates simulated in the tunnel wi th those observed indicate that this hydrothermal method is a useful tool f or predicting water inflows in underground works.