Prevention of Freshwater Breakthrough into Potassium Mines

Abstract

The exploitation ofpotash salt deposits is associated with a need to protect mines from freshwater breakthroughs. Advanced monitoring tools and calculation methods make it possible to identify areas that can be dangerous due to discontinuities in the waterblocking stratum, separating the water-bearing horizon from the mined-out area. This is the first time that a method for preventing freshwater breakthrough into mine workings has been proposed and it is currently at the design stage. A hazardous area is isolated by constructing bulkheads and the mined-out space is then filled with relatively saturated brines. Since the freshwater density is lower than the density of the brines, even if the continuity of the waterblocking stratum is disrupted, then the freshwater will not flow into the mined-out space and so it will not lead to massive dissolution of the salt rock. At the same time, the brines pumped into the goaf are not completely saturated with NaCl and KCl. They will be saturated already during mine flooding. We estimated the negative consequences associated with the elimination of a dangerous area using integrated filtration-migration and geomechanical numerical modelling. According to the computed results, we localised the zones within which the elimination of a potentially hazardous area causes an increase in the human-induced impact on the waterblocking stratum and imposes the threat of destruction. To minimise the risk of discontinuity of the waterblocking stratum in the submerged western part of the potentially hazardous area, it is recommended that saturated brines are used to fill it. The implementation of these measures will make it possible to reduce the degree of dissolution of the salt rocks in this area and reduce the human-induced impact on the layers of the waterblocking stratum.