Abstract: An arch useful for withstanding effects of rock burst occuring in underground mines/tunnels. The arch comprises a curved U-section arch provided on both ends with slidingly coupled U-section arch pieces, the coupled top and bottom pieces being provided with at least two guides on both sides. The guides are slidingly coupled with the bottom section aches, the ends of the top section arch being placed on upper holder plates, the upper holder plates being fixed with the bottom sections on both sides. The bottom portion arches also having at least one lower pair of holder plates fixed on both sides below the upper holder plates.

Abstract: Shortwall mining equipment for extraction of some pillars in an underground coal mine has a series of self-advancing powered roof supports (1) for placement along the pillars (2) under extraction, the pillars under extraction being located within a panel (3) which is surrounded by barrier pillars (4), an armoured face conveyor (5) fixed to the barrier pillars, a light duty chain conveyor (18) and a belt conveyor (19). Each of the self-advancing powered roof supports (1) has at a goaf end a support mechanism (6) on a base frame (14) with a side shield (7) and hydraulic ram side arms (10). The base frame (14) is provided with front and back side hooks (11 & 12) to facilitate pulling of the support mechanism (6). The armoured face conveyor (5) is provided with a shearer (15) having a cutter drum (16) coupled with a centrally located ranging arm (17), an outbye end of he armoured face conveyor (5) being at a right angle to and set upon the light duty chain conveyor (18) as a freely advancing bridge.