An analysis of chamber filling effects on the remediation of flooded gypsum and anhydrite mines

Abandoned gypsum and anhydrite mines can be filled by underground water that progressively dissolves pillar rock. The long term stability of the mine under the weight of the overburden is therefore jeopardised. A common remedial measure consists in filling the flooded chambers with granular materials. The aim of the paper is that of investigating the effect of the mechanical characteristics of the filler on the time of mine collapse, induced subsidence and pore water pressure generation. By means of Sharp Front theory the saturation front advance and the loss of pillar bearing capacity with time is determined first. Subsequently one dimensional consolidation theory is used for the determination of the proportion of overburden weight carried by the solid skeleton of the filler and by water pressure. A parametric analysis is eventually performed for the case of an abandoned gypsum and anhydrite mine in order to determine the most appropriate mechanical characteristics of the filler material.