New design of tubbing ring especially suitable for tunnel in gravely environs with no ground water

摘要

The new design of a tubbing ring consists of two U-shaped metal profiles (1, 2) holding several transversally positioned rows of square wooden bars (3). The bars are held in place by small iron squares (4) which are welded to both ends of the profiles. Metal fish plates (5) with bores (6) for the insertion of screws are welded to the upper side at both ends of the profiles. The U-profiles are bent to match the shape of the tunnel.