Hydraulic Coal Mining

the underground working of coal deposits in which the coal is excavated, transported, and lifted to the surface by using the energy of a water jet. The source is usually underground water flowing into the mine.

The first experimental operations with hydraulic coal mining were carried out in 1935-36 by V. S. Muchnik in the Kizel coal basin; from 1938 to 1941 it was used in the Donets Basin (Donbas) and in the Kuznetsk Basin (Kuzbas). It was put on a commercial basis in the mines of the USSR in 1953 with the Polysaevo-Sever hydraulic mine in the Kuznetsk Basin. Between 1965 and 1967 major hydraulic mines began operations in the Donbas and the Kuzbas with all technological processes mechanized (Baidaevka-Sever, Gramoteino 3-4, Krasnoarmiia No. 1, and Krasnoarmiia No. 2).

In hydraulic coal mining the coal bed is broken down either by means of a high-pressure water jet (5 to 10 meganewtons per sq m), which is formed by monitors, or by means of mechanohydraulic machines (mechanical breakdown of the coal with subsequent washing out by the water). The water is supplied to a stope through pipes from centrifugal pumps. The coal that has been broken down in a stope is washed off by the water and transported along metal channels laid out in the mine workings that run with a slope of 3° to 3.5° to a central chamber of a hydraulic lift. From here the water-coal mixture is transported to the surface and then to a concentrating mill, where the coal is concentrated, dehydrated, and dried.

The methods used with hydraulic coal mining include mainly sublevel hydraulic breakdown, hydraulic breakdown from headings, and mechanohydraulic excavation from headings or longwall drifts. The coal is excavated, as a rule, from short stopes without timbering the worked-out space. On steep and sloping (over 25°) seams the sublevel hydraulic breakdown is used, part of the mine area being divided by headings into blocks of 150 to 200 m in length along a line of bearing and a dip of 80 to 120 m. Within a block at distances of 6 to 12 m, sublevel drifts are driven one after another; the coal pillars formed by the drifts are broken down from the bottom upward by monitor jets. For gently sloping seams (up to 15° or 18°) the coal is usually broken down from the headings. In this case the mine field is divided into blocks up to 1,500 m in length along a line of bearing and a dip of 800 to 1,200 m. In turn, the blocks are divided along the dip into tiers by storage drifts that are driven every 200 to 250 m. From these, headings are driven along the uprise of the seam every 12 to 15 m. The coal pillars between them are removed by monitor jets or by a mechanohydraulic combine. With the appearance of high-productivity combines for mines using the usual dry technology on mildly sloping seams, mechanohydraulic excavation from long walls is employed in certain cases. The plan of the mine field preparation and the sequence of mining operations are similar to the ordinary technology except that the coal is transported from the combine by a stream of water.

The technical-economic factors are better in hydraulic mines than in dry mechanized mines under the same mining conditions (for instance, labor productivity is 1.5 to 2 times higher). Improvements are being made, such as the development of new technological schemes for excavating, transporting, and dehydrating the coal, the increase in productivity of hydraulic cutting to 80 or 100 tons per hr, the use of programmed control, and the use of mechanohydraulic machines.

Hydraulic coal mining is used not only in the USSR, where over 8 million metric tons of coal (1970) are obtained by this method but also, based on the Soviet experience, in the People’s Republic of China, Japan, the USA, Poland, Czechoslovakia, the Federal Republic of Germany, and other countries.