Mine shafts in Nord and Pas-de-Calais coalfield, France : risk assessment and treatment technique
Résumé
In France, coalfield abandonment is controlled by legal procedures that require owners to identify and assess residual risks associated with the underground mine workings. If necessary, treatment techniques must be defined in these assessments in order to mitigate the associated risks for the population and future land planning. The main risks associated with mineshafts are the sudden collapse of their column, gas explosion, asphyxiation and/or intoxication. The Nord and Pas-de-Calais coalfield extends 100 km from east to west and 15 kin from north to south. Coal exploitation induced the sinking of more than 600 shafts from 1716 to 1960 spread over 41 coalfields. The present paper describes the work accomplished by Ineris and the French Coal Board (Charbonnages de France) for mineshaft vicinity security. The first section covers risk assessment methodology and aims to identify and evaluate the risks associated with mine shafts. The great number of shafts has led Ineris to develop a methodology to ease the analysis. The present study then discusses the techniques involved in the treatment of, mine shafts in Nord and Pas-de-Calais coalfield which must be adapted according to the risk assessment as well as the surface occupation.