Many older tunnels today are either not used to their full potential or are not used at all due to their structural condition. These older tunnels can be widened in order to accommodate larger freight trains, trucks, light rail or to increase the traffic capacity and in the case of leaking tunnels and deteriorated tunnels can be rehabilitated creating a dry and safe environment.
Tunnel widening can be accomplished utilising the principals of NATM/SCL/SEM. After appropriate pre-support is installed, the existing tunnel lining is removed in sections and a new shotcrete lining is installed. In order to preserve the quality of the tunnel inner lining as well as the utilities and finishes in the tunnel, a waterproofing system is installed against the shotcrete lining then the inner lining is constructed.