Development of technology for additional extraction of potash ore reserves from previously mined out panels at the depths exceeding 600 metres of the Starobin potash salt deposit

Abstract

Studied the possibility to extend the life of the Production Unit no. 3 mine of JSC “Belaruskali” through the additional extraction of sylvinite ore reserves left in the previously mined panels of the mine field of the 3rd potash level. It was determined, that during the period from 1971 to 1980 a considerable part of the southern direction of the mine field on the area of more than 5,3 million m2 was mined by the roadways on the layers 2, 2–3, 3 without the mining of the 4th sylvinite layer. The volume of the leftover reserves of minerals in the mined panels makes more than 22 million tons. There is direct access to these panels from the main southern gates. As a study result of geological structure of the mined panels it was determined that under the influence of rock pressure the undermined sylvinite layer no. 4 took the form of a wave-shaped seam with the capacity of about 1 meter which rests on compressed inter-chamber pillars and on compressed rocks of layers 2, 2–3, 3 of destroyed inter-roadway pillars, which fills the space of the roadways. Such geological structure of the seam enables to extract minerals using the technology of selective layer mining by successive top and bottom faces. As a study result of the stability of the mine workings performed along the roadways and inter-chamber pillars under conditions of different roof positioning, it was determined that during the preparation of the faces the most advantageous locations for development workings are the areas previously mined by the room and pillar mining system. In this case, the highest stability of mine workings located in the stopes of the room and pillar mining system will be provided by their roofing location with cut of 0.15 m of the 4th sylvinite layer. When this occurs, their predicted life without repair, even without the use of special protection methods, would be between 3.5 and 8 years. Based on the results of the study, a conclusion was made on the technical possibility and economic feasibility of additional extraction of sylvinite ore reserves left in the western panels of the southern direction of the mine field of the 3rd potash level of the Production Unit no. 3 mine, finished over 40 years ago by the room and pillar mining system using selective layer mining technology by the longwall faces. With minimal capital, organizational and technical expenditures, the extraction of these reserves will allow the company to produce additionally 5.5 million tons of potash fertilizers.