a self-pouring device for draining water-flooded rock (mainly sands). The filter is installed in a hole up to 15 m long to drain the rock lying above the roof of a horizontal or inclined mine working or the roof of a yard near a shaft or to relieve the pressure of headwaters on the bottom of a mine. In the USSR pile filters were first used in 1931 in the Moscow Area Coal Basin; they are commonly used during the sinking of shafts and subsurface drainage of quarries.
A pile filter consists of a perforated metal pipe (1 m long, usually 32 mm in diameter) and subfilter pipes (of the same diameter, with sections 1 m long). The filter discharge in cases of a water-saturated level during the initial drainage stage reaches a rate of 4–5 m3/hr but decreases gradually as the level becomes lower. The water is discharged systematically from the filter through a rubber hose to an overflow or drainage chute or to the drain of an area catch basin.
V. A. POLUIANOV