Exemple d’impacts de l’arrêt de l’exploitation minière et de l’exhaure dans le bassin houiller de Faulquemont (Lorraine)

Abstract

A rock-mass mined by underground exploitation can be assimilate as an aquifer reservoir which is not delimited by physical boundaries unlike a geological reservoir. In fact, this ground-water reservoir includes the residual mining voids and mining works (drifts, shafts, galleries), natural porosity (interstitial porosity and of the natural discontinuities) of the fractured rock-mass, including the fracturation induced by mining. Firstly, this communication present the results obtained with two different methods used to evaluate the total volume of the residual mining voids and compare these results with the volume of water flooding calculated from the curve of the underground water level rise measured in the Faulquemont coal basin (Lorraine). The second part of this communication explains the effects of water level rise on the stability of the surface. Indeed, the water level recovery, when pumping is stopped, can induce a rise of ground level. The studies concerning mining respectively in The Netherlands and in Germany highlighted this phenomenon. The observations made also in the district of Faulquemont, where the works flooding has been stabilised, give similar results. No consequence on buildings and surface infrastructures due to this phenomenon has yet been noticed.