Analysis of the long-term stability of an ancient room and abandoned pillar mine - Impact of the water level

International audienceThe recent mine water level rise in the iron mines of Lorraine (France), due to their abandon, was followed by several subsidence events. FLAC-2D has been used to analyse the stability of a former two-level room and pillar mine, in order to predict the extent of the failure zone, depending on mechanic property and geometry modalities (bad superimposition of the pillars in the two seams particularly). The model successively simulates the water level rise then the long-term strength reduction, which is partially due to the rock resaturation. The long-term stability diagnostic expressed by the experts is confirmed in whichever geometrical configuration of the exploitation, and whatever mechanical properties are used. Nevertheless more precise characterizations of the hydromechanical behavior should be planned for more critical sites to improve the evaluation of the mine failure hazard