The use of shotcrete to build new concrete structures as well as to restore and repair existing structures is well-known and documented. Although this versatile method of placing concrete is widely accepted by the construction industry, shotcrete for ground support in tunnel and mine operations is perhaps less known in the general construction community. Underground shotcreting, however, consumes the largest volume of concrete of all pneumatic applications. Today, nearly all tunnels under construction in North America will use shotcrete as part of their support system. And rather than cast-in-place concrete lining, a shotcreted final tunnel lining, installed after the ground support system is in place, is also practical and gaining acceptance.
Some factors important to successful tunnel shotcreting include:
- A clear understanding of the concrete components and mix design.
- A clean rock surface to ensure bonding of the concrete and filling of fissures and surface breaks.
- Careful planning of the batching, transport, and application time of the concrete based on the logistics of the project.
- A familiarity with the conditions and safety requirements of the underground environment.
- Proper and ample training and education. This is not a "do-it-yourself" construction method!