Relation between temperature and intensity of groundwater circulation in Alpine massifs as a tool for predicting water inflows in underground works
Résumé
Numerous long tunnels have been and will be drilled at a large depth in mountainous massifs. The monitoring of water inflows temperature in five long alpine tunnels (Vereina, Gothard-N2, Mont-Blanc, Simplon et Gothard-AT) shows that the water temperature in underground works is strongly dependent on massif permeability and groundwater flows. Cold waters coming from high infiltration zones have a refrigerating effect on the massif. Thus, measuring water temperature during drilling constitutes an efficient and cheap predicting tool of water inflows. These inflows can be localisated inducing a local decrease of temperatures in the massif, or they can be diffuse and induce a global decrease of the water thermal gradient in the massif. A negative correlation between the water thermal gradient in each studied massif and the intensity of water inflows observed later in the tunnels intersecting them has been shown.
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