Improved Technology with Backfilling in Potash Mines

The development of potash deposits is generally accompanied by large losses of minerals in the subsurface. The main reason for these losses is the use of a room-and-pillar mining system, where left pillars hold the overlying rock strata and aquifers located above the productive seams. Over time, the bearing elements of the mining system begin to deteriorate, leading to a loss of continuity of the water-protective stratum, the formation of water-conducting fractures, salt dissolution, and consequently, the flooding of the potash mine. The most effective method for solving production problems in the field of increasing mineral recovery and mine safety is the introduction of backfilling technology. The aim of the study is to identify the effect of backfilling on the stress–strain state of the rock mass in the vicinity of stopping and backfilling operations, to develop a technology for potash ore extraction with increased recovery, and also to solve the fundamental issue of the proposed technology, namely, the transport and property considerations of the backfill mixture. Numerical modeling methods and analytical derivations of calculation formulas for backfill mixture transport are used in the work. A comparison of dry, hydraulic, and hardening backfill mixtures is carried out. The study established that hardening backfill ensures a faster transition to the stage of mining the remaining reserves. A technology for pillar extraction with the leaving of technologically necessary narrow pillars is proposed, allowing for the safety of mining operations. Formulas are derived for calculating the required strength of the backfill based on the loading degree of the technological pillar. Transportability criteria are formulated, and a calculation procedure for pipeline transport parameters under gravity and gravity-pneumatic modes is developed. The proposed technology for potash ore extraction with hardening backfill allows for increased mineral recovery while maintaining safe conditions for undermining the water-protective stratum.