METAL TRAPEZIUM-LIKE SUPPORT OF PREPARATORY WORKINGS

摘要

A metal trapezium-like support of preparatory workings wherein a rectangular roof beam rests with one end on the post near the side of the working, and with the other end – on the rock massif of the working of the other side. The straight continuous roof beam rests with one end on a wooden post installed on the berm near the side of the working, and with the other end on metal post at the other side.