ABSTRACT
Tunnel linings in rock may be formed using shotcrete, pre-fabricated segmental concrete, or cast-in-place concrete. The main purpose for the use of shotcrete for final lining of hydraulic tunnels is for protection, and not long term structural requirements, to prevent scour and erosion of non-durable rock conditions which typically exists in discrete locations along a tunnel alignment. The design of shotcrete final lining for a hydraulic tunnel should be carefully reviewed by an independent tunnel consultant prior to the commencement of all final lining works. The majority types of tunnels in rock for infrastructure include an operational requirement to prevent water ingress with complete watertightness in order to limit hazards of slipping, ponding, and ice formation. The most common and cost-effective form for the prevention of water ingress in tunnels is the application of waterproofing by use of fabricated polyvinyl chloride (PVC) sheeting membranes or spray-on coatings.
