Grain-size control in coal and carbonate rock mining

Abstract

The prime cost of coal and carbonate market products depends on grain size composition and strength characteristics of minerals produced. The grain size composition of mineral products is governed by geological structure of deposits and by mineral mining technology. The volumes of geological blocks and grain size distribution in bedded deposits are conditioned by density of natural joints. Blastless mining technologies applied in coal and carbonate deposits produce block sizes which are much less than natural block sizes in rock mass. It is possible to change the actual/natural block size ratio by selective preparation of different mineral layers to extraction with appropriate choice of mining and handling equipment. The grain-size control and preservation of strength characteristics of rocks is possible using specialpurpose blasting techniques and improved extraction-and-loading technologies. In particular, buried blasts at a powder factor of 0.10–0.15 g/m3 make it possible to split a rock mass layer along a system of natural joints. The buried blasting experience is gained in mining operations in Ekibastuz and Shubarkol coal fields, in Dobryatinsky and Kasimov limestone deposits, and in other mineral extraction projects. In order to simplify extraction of heterogeneous layers, it is suggested to reduce the height of an extraction panel to 1.5–5 m and to employ hydraulic rear shovels with special-design buckets in extraction-and-loading.