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A rib and lagging tunnel is formed by constructing rings made of wide flange beams which support a ring of wood lagging.
Once a rib is installed, it is expanded. This expansion compacts the material or steel outside of the tunnel eliminating the need for grouting. These tunnels can be built in a variety of shapes including round, square, and arch.
Rib and lagging tunnels are best suited for cohesive soils. The face of a rib and lagging tunnel can be excavated through Hand Tunneling or Machine Tunneling as long as a full tunnel shield is utilized. (see Hand Tunneling and Machine Tunneling).
Rib and lagging tunnel |
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