Kinematics and thermal conditions in the permafrost-affected rockwalls of the Aiguille du Midi (3842 m a.s.l., Mont Blanc massif, France).
Résumé
Processes that control climate-dependent rockfall from permafrost-affected rock slopes are still poorly understood.In this study, we present the results of a Wireless Sensor Network, integrated within the Swiss project PermaSenseand developed in 2012, to measure rock temperature and geotechnical parameters in the steep rockwalls of theAiguille du Midi (AdM, 3842 m a.s.l., Mont Blanc massif, France). Accessible year round by cable car, the AdMcomprises two main peaks: (i) the Piton Nord with the cable car arrival station, where 4 crack-meters are placed onfour major fractures, and (ii) the Piton Central with many touristic infrastructure, equipped with three 10-m-deepboreholes with 15 temperatures sensors since 2009, and where 2 crack-meters are installed along a major fracture.Three major kinematic regimes are observed: (i) opening of clefts when the rock temperature becomes positive,followed by closing during the cold period, (ii) summer opening continued by a winter opening, and (iii) closingduring the warm period followed by opening in winter.