GFRP reinforcement for segmental linings of mechanized excavations
The use of GFRP reinforcement is gradually spreading to replace or to integrate the traditional steel rebar for tunnels excavated with shielded TBMs and lined with a precast segmental lining.
The complete replacement of the steel rebar with GFRP is particularly used for segments that have to be demolished after their installation, for example for cross-passages or niches realization. In this regard, some examples of their application and of their dimensioning and the results of laboratory tests are described.
GFRP reinforcement cages placed on segments' edges can play an important role to limit the number of cracks and local breakages caused by impacts and unforeseen load conditions, mainly before and during the lining installation.
Some laboratory tests were carried out to show the GFRP reinforcement effectiveness. The analyses' results on a 3D model, which allowed to consider the contribution of such reinforcements both during the lining erection and the service (described below), show that it is possible to increase the lining strength extending the GFRP reinforcements to the whole segments' perimeter. This has to be carefully analysed to optimize the lining total cost, considering repairs and waste costs.