Precast tunnel segments reinforced with fibreglass bars

The possibility of substituting the traditional steel reinforcement with fibreglass bars in precast tunnel segments is investigated herein. Precast segments are traditionally used for the lining of tunnels excavated with a Tunnel Boring Machine (TBM). The use of fibreglass reinforcement in tunnel segments has several advantages, mainly related to the durability aspects. In particular, there is a possibility to reduce the concrete cover that is usually a weak point for this kind of structure (concrete cover can crash during handling of the segments or due to TBM thrusts). Furthermore, the use of fibreglass bars is suitable in tunnels where the aspect cycle life is equal or higher than 100 years. In addition, the proposed solution is suitable in the part of the tunnel that have to be eventually removed (typical problem in TBM tunnel). In this case, segments reinforced with fibre bars can be easily demolished and disposed. Full scale bending tests have been performed on precast segments in order to compare the structural performance of fibreglass reinforced concrete with respect to traditional steel reinforced concrete. Furthermore, consideration on the design procedure for the proposed solution is highlighted.