| 摘要 |
A support structure for the wall and/or roof of a tunnel comprises lagging boards 4 positioned between and supported by metal supports 2 in which struts 6 or tensioned bolts or wires connect adjacent metal supports 2 to form a rigid structure which will dissipate external loads thereby minimizing the strain on individual metal supports 2. The metal supports 2 can be considerably lighter than heretofore without sacrificing safety standards. <IMAGE> |
