Abstract: A variable wall mining machine to release coal from a longwall mine face includes an articulated auger assembly made up of a plurality of side-cutting auger sections joined together by universal couplings in an end-to-end relation and coupled to a drive at one end of the assembly. A scavenger plow, supported on the mine floor, consists of sections connected together for articulated movement toward and away from the longwall mine face. Two support arms are journaled by bearings to each auger section and the other ends of the arms are pivotally supported by one of the scavenger power sections. Hydraulic actuators, supported by mine roof supports, move two adjacent scavenger plow sections together with two auger sections as a pair into sumping cuts with the longwall mine face. Other hydraulic actuators supported by the scavenger plow control the elevation of the pivotal arms and, hence, the auger assembly coupled thereto for shear cutting the mine face.

Abstract: An arched roof support for a mine opening essentially includes an elastic plate member with a preselected curvature across its length employed for establishing a prestressed emplacement into a load-bearing contact along the middle portion of the roof stratum of the mine opening. The material forming the plate member is selected for withstanding an elastic deformation force to maintain the prestressed emplacement which is effected by the elevated support of one or both sides of the plate member along or toward side ribs of the mine opening. As anchoring means, the side edges of the plate member are either supported solely by the ribs of the mine opening or additional support is supplied by roof bolts, rib bolts or props having an adjustable length. A hydraulic or mechanical actuator is used to elevate one or both side edges of the plate member to its emplacement elevation whereby the side edges have been raised to between two-thirds to three-quarters of the height of the mine opening or at the roof surface.