A reinforced lightweight mine door for installation in a mine passageway. The mine door includes a generally rectangular sheet metal door panel having four sides and four corners, and a reinforcing structure projecting from a face of the door panel. The reinforcing structure has a central section and a plurality of channel sections extending from the central section toward respective sides or corners of the door panel. A mine door including at least one hinge arrangement having unique reversibility features is also disclosed.

A retainment wall for underground horizontally extending mine shafts wherein a spaced vertical series of horizontal support ribs are secured to one or more upright supports that are secured in the mine shaft between the side walls thereof. Porous material covers and is secured to the forward retaining face of the wall structure. If the retainment wall structure is to be used as a fill retainment barrier the porous material is spray coated with a settable sealant which covers the forward face of the wall structure and the perimeter thereof to seal off the mine shaft.