Nonlinear modeling of high-performance fiber-reinforced concrete in tunnels: evaluation through field and laboratory testing

The design of fibre-reinforced concrete structures must follow the design principles concerning limit states, similar to those adopted for conventionally reinforced concrete. However, the use of linear elastic analysis or conventional yield-line theory may, in many cases, underestimate the benefits of fibres in providing greater load-bearing capacity, particularly when high-performance steel fibres are adopted. This paper presents two case studies of real tunnel projects in which the author was involved, where the use of non-linear modelling of steel fibre-reinforced concrete elements, coupled with physical testing, provided significant benefits in the design and construction of tunnel linings. The first case focuses on the design of thin tunnelling linings using rock-bolted shotcrete. In this case, the non-linear modelling coupled with full-scale field tests demonstrated load-bearing capacities up to 6-7x greater than conventional design methods. The second case presents the design of a segment lining and the effects of fibre reinforcement on the bursting and splitting capacity of longitudinal joints under rotation. In this case, non-linear modelling coupled with laboratory testing on large-scale segment joint samples demonstrated that conventional reinforcement was unnecessary, whereas analysis with linear-elastic theory indicated otherwise.