Safety of a water-proof pillar between the stoping void and the aquifers defines the key feature of water-soluble mineral mining. In this regard, the most important element of geomechanical supervision of mining operations, especially, at the mine project stage, is the engineering safety criteria aimed at the adequate valuation of safe undermining of water-proof strata (WPS). The WPS safety procedures now in force calculate only maximal sagging of undermined beds and disregard deformation in the edge area of WPS. In the meanwhile, the edges of WPS are the areas of localization of maximal horizontal strains, and the hazard of vertical jointing is the highest in these areas. In this connection, in the capacity of the index of the manmade load on WPS, it is proposed to use the maximal slope of the edge area of the subsidence trough. The evaluations were carried out in 6 Uralkali’s mine sites selected from the mathematical modeling and geophysical survey data which exhibited considerable damage of WPS. Based on the implemented research and justifications, it is recommended to use the generalized safety criterion for undermining of WPS as a maximal subsidence/mining depth ratio which is directly proportional to the ground slope. This engineering procedure describes more adequately the fracture mechanism in WPS rocks, in particular, damage localization in edge areas of the subsidence trough, or influence of mining depth on WPS stability and, which is main thing, is based on the criteria derived from the long-term observations and measurements performed in the Upper Kama deposit. The study was supported by the Russian Science Foundation, Grant No. 19-77-30008.
Management of mine sites after closure
