Drainage of Mineral Deposits

(also mine drainage), a set of measures used to pump out increased inflow of underground water during the construction and working of mines and quarries. It is necessary to drain mineral deposits, because such deposits frequently occur in flooded areas (such as the Moscow Area Coal Basin, Dnieper coal basin, the iron ore deposits of the Kursk Magnetic Anomaly). Water inflow in coal mines under construction is as much as 3,000 cu m per hr (for example, mines nos. 49, 50, and 53 at Poplevinskii); in opencut mines it is up to 3,600 cu m per hr (the Lebedinskii iron ore opencut mine), and in subterranean mines as much as 12,000 cu m per hr (the Mirgalimsai Mine). Capital investment for drainage reaches 15–20 percent of the total mining cost in the USSR, and operating expenses amount to as much as 25–30 percent of the prime cost of extraction.

Drainage of mineral deposits increases the stability of the rocks, prevents running ground, and keeps large quantities of water from flowing into excavations. Such drainage is carried out by partially or completely draining the rocks of the roof and the mineral deposit itself and by reducing the pressure of the underlying water-bearing horizons to safe levels. The drainage is coordinated with mining work; it is done before the excavations are made (preliminary drainage) and simultaneously with the excavation and cleanup work (concurrent drainage).

Among the the drainage methods are surface (shaftless) drainage, which is carried out from the earth’s surface, subsurface drainage, which is carried out underground, and combined drainage, using both methods. Surface drainage is accomplished by means of drainage and inverted wells, trenches, closed drains, and needle filter devices. Subsurface drainage is carried out by means of flow-through and pile filters, drainage wells, and recovery shafts. In this method, water is usually fed into the mine excavations by drain systems and subsequently delivered to the surface by a shaft drainage system. Combined drainage employs the techniques of both methods together.

Mineral deposits are drained by means of drainage devices that lower the water level on civil engineering projects, such as lightweight and ejector-type needle filters and open drainage systems. One type of mine drainage lowers the water level while the shafts of the mine are being cut; this involves the use of drainage wells and sometimes horizontal pile filters, overhaul needle filters, and water level lowering wells.

The practice of draining mineral deposits developed in the USSR in the 1950’s when industry began producing powerful shaft pumps, drilling machines, needle filter devices, and other equipment. The theoretical foundations for mine drainage are developed in mining hydrogeology.