Ring Beams & Lagging
Rib and Lagging is a primary tunnel liner used to shore horizontal excavations in soft ground. A rib and lagging tunnel is formed by constructing rings made of wide flange beams which support steel or wood lagging. Once a rib is installed, it is expanded in place. This expansion compacts the material outside of the tunnel eliminating the need for grouting. These tunnels can be built in a variety of shapes including round, square and arch.