Borehole Hydraulic Mining

a technique used in underground extraction of a solid mineral, in which a solid mineral is broken up and delivered to boreholes by water and removed to the surface as a hydraulic mixture. Borehole hydraulic mining is used primarily to extract loose and weakly cemented ores, such as phosphorite deposits that occur in layers relatively close to the surface.

Borehole hydraulic mining involves drilling wells ranging from 100 to 300 mm in diameter. The ore body is broken by the hydraulic pressure gradient in the case of very loose and greatly flooded ores and by a stream of water otherwise. In the first instance, the water in the layer is pressurized in one group of wells and the pulp is pumped out of neighboring wells; in the second, water under pressure is fed into the nozzles of a monitor.

The destructive action can be intensified by means of vibrations or explosive charges; alternatively, the ore body can be weakened at the start of mining operations by chemical or microbiological methods. The hydraulic mixture is brought to the surface by a hydraulic elevator, an air lift, or an air lift combined with a hydraulic elevator; it can also be brought to the surface through the creation of excess pressure in the layer.

Borehole hydraulic mining makes it possible to work deposits occurring under bodies of water. It ensures a smooth flow of operations and allows automated processes to be used.