Technical solutions for soil nails in tunnel face reinforcement and drainage

Tunnelling in soft ground conditions requires the adequate stabilization of the tunnel face. To this target, the soil nailing is one of the most effective techniques. In this paper, some innovative technical solutions are discussed, purposely devised to improve the reinforcing action and to couple it with an additional drainage action. In particular, a new fibreglass pipe is described, characterized by a preformed corrugated surface which improves the mechanical interaction with the injected grout. Some comments about its performance are drawn from the results of pull out tests. In addition, details on a new type of soil nail for coupled reinforcement-drainage action are given.