Lattice girder to support tunnel wall - has at least three longitudinal sectional steel members with flat sides connected via e.g. U=shaped crossing diagonal bars welded thereto

摘要

The lattice girder is intended as a support in an underground e.g. mining cavity. It acts as a reinforcement for a subsequently applied concrete lining. It comrpises at least three approximately equi-spaced longitudinal members (10-13) rigidly connected via diagonally crossing bars (14,15; U-shaped bars 14,17,14 and 15,16,15'). The upper members (10,12) and/or the lower members (11,13) consist of sectional steel with at least one plane side with the bars (14,15) welded thereto. The upper members (10,12) may be U or T-sections or flat strips and the lower members (11,13) may be round sections or flat strips. ADVANTAGE - The arrangement eliminates welding problems presented by prior art, facilitates adapting the load bearing grider to the contour of the cavity, and does not present more 'shadow' areas difficult to fill with sprayed concrete than prior art.