In a major fault zone under more than 1000 m of overburden in the 24.5 km long Laerdal Tunnel, Norway, large deformations have occurred in squeezing rock a long time after excavation. Heavy support including rock bolts, many layers of Fibre Reinforced Shotcrete (FRS), and reinforced ribs of sprayed concrete (RRS), were installed during construction. Cracks started to develop in the FRS and the RRS due to large deformations. Several layers of FRS were applied during the next 6 weeks as the cracking continued. The total thickness of FRS applied was 95 cm in the crown and 60 cm in the walls. In spite of this, the convergence continued, and sheared and crushed both the FRS and the rock to a depth of at least 150cm behind the shotcrete. In this case, the FRS behaved very similarly to brittle rock and the fibres had only a minor effect on behaviour during development of cracks. However, the fibres prevented release of concrete slabs from the crown. During shearing a large number of the fibres were cut off, while most of the fibres were pulled out during bending failure.
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