Verification of Serviceability for Steel Fibre Reinforced Concrete in Tunnelling

For permanent linings of the tunnel constructions common today, which are made of watertight concrete, reinforcement is necessary. It has the function of preventing wide cracks in order to avoid inflow of water. Using steel fibre reinforced concrete (SFRC) watertight constructions without steel bar reinforcement or a separate sealing is possible. Several thousand metres of tunnel have already been constructed in Germany in this way. The ability of SFRC to react in a plastic way to bending moments is the reason for the great potential of this material. A special design method conforms to the material properties of SFRC is introduced in this article. On the basis of a bending test carried out according to DIN 1048 the cracking behaviour and the watertightness of this concrete can be proved. A new test method is introduced for the determination of crack widths.