Coupled processes involved in post-mining
Abstract
Long term evolution of abandoned underground mines in terms of stability and environmental impacts depends on hydro-mechanical and geochemical processes involved in the interactions between rocks, water and air. These coupled effects are discussed on the basis of the results of field investigations, in situ and laboratory experiments as well as modeling. In particular the closing-induced mine flooding effects on ground movement, overburden collapse and ambient air composition are analyzed. It comes out from this analysis that mine flooding can result in ground uplift. This phenomenon is explained by poro-elastic behavior of the overburden. Moreover re-distribution of effective stresses can induce some convergence of cavities walls and reduction of mechanical properties of rocks. Besides, flooding may lead to a change in the composition of air present in mining reservoirs. Connected to surface through fractures and other pathways, air poor in oxygen and eventually containing undesirable gases (methane, radon) can be harmful for the persons staying in the insufficiently ventilated buildings. These results allow to conclude that appropriate comprehension of hydro-mechanical and geo-chemical coupled mechanisms involved in mine closing and post-mining is essential for prevention and management of hazards.