a unit for mineral extraction and tunneling in underground workings by pumping water under pressure to the crushing zone. It was first proposed in the USSR (1948). There are four types of mechanical-hydraulic machines: with a mechanical crushing member, with a member in the form of fine jets (at a pressure of 5–50 meganewtons per sq m [MN/m2] for coal and 50–200 MN/m2 for rock), with an impulse member (at a pressure of 300–1,000 MN/m2), and with a combined (mechanical and hydraulic) member.
A mechanical-hydraulic machine consists of the working member, running gear, a water-supply system, and a hydraulic control; the material removed from the working face is usually transferred by a nonpressured hydraulic system. The main advantages of a mechanical-hydraulic machine are the absence of electric power at the mining face and the complete elimination of dust. The most promising type is the machine with a combined working member. Efforts to develop and improve mechanical-hydraulic machines are being made in the USSR, the Polish People’s Republic, the USA, Canada, Great Britain, Japan, and the Federal Republic of Germany.
M. N. MARKUS