TECHNICAL | LININGS - FRC
and contributed to a lower carbon footprint. The hybrid SFRC option also accelerated construction. The time required to fix corbel reinforcement was estimated to fall by around 30% to 40%, mainly because the solution removed clashes at the bonded-anchor and reinforcement-cage interface and reduced transverse conflicts during cage installation. The West Gate Tunnel corbel application shows how close collaboration between design and construction teams, supported by advanced computational analysis, can deliver measurable savings. In this case, a 38% reduction in conventional reinforcement improved cost and programme outcomes, while the reduced handling of heavy and congested reinforcement also supported better health and safety performance.
Jansen Mine, Canada.
UNDERGROUND SPACE Slipforming Shaft lining offers another promising field of application, such as at the Jansen Mine in Canada. In this application, the shaft walls are slipformed, with a planned production rate of up to 9.84ft/day (3m/day), according to figures from US consultant Arup. Wall thickness varies from 2.62ft (0.8m) to 3.60ft (1.1m), with an internal diameter of 27.90ft (8.5m). The specified concrete strength is 60 MPa, with a fibre dosage rate of 67 lb/yd³ (about 40 kg/m³). In the UK, following extensive research and development,
Above right: ECO Caverne® Image courtesy of ECCUS.
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CECL Global, under the leadership of Professor Colin Eddie, has been developing its ‘Slipform Tunnelling’ system which combines a new mechanised shutter with a novel lining material. The next-generation tunnel construction technology combines continuous excavation with the installation of the high-performance permanent lining, pressed into place in a one-pass solution. The system would use an articulated slipform shutter around which the specially formulated lining material is injected, under pressure, to create a watertight and durable structural lining. A variation of the system would not involve excavation but focus on relining of existing tunnels.
REFERENCES
● fib Bulletin 105 — Fibre Reinforced Concrete, state-of-the-art report, Task Groups 4.1 and 4.2, November 2022.
● fib Model Code for Concrete Structures 2020. Lausanne, Switzerland: fib, 2023. ● fib Bulletin 116 — Fiber Reinforced Sprayed Concrete in Tunnels and Underground Spaces, Working Party 1.4.3, April 2025.
● AFTES GT6.R5A1 — ‘Wet-Mix Sprayed Concrete for Permanent Application in Underground Structures: Principles and Specification Guideline’, April 2026.
● fib Bulletin 87 — Precast Tunnel Segments in Fibre-Reinforced Concrete, state-of-the- art report by Working Party 1.4.1, Commission 1 – Structures, 2017.
● ACI Committee 544. (2016). ACI 544.7R-16: ‘Report on Design and Construction of Fiber-Reinforced Precast Concrete Tunnel Segments’. American Concrete Institute.
● Handbook of Precast Segmental Tunnel Lining Systems; Ed. Nasri, V; Klug, D; Fulcher, B & Morrison, J.A.
● Lu, L; Chong, A.K.T.; Alaedini, H.; Ngan, A.; Barry, J. & Hii, K. (2023) ‘Steel Fibre Reinforced Concrete and its Application as a Load Bearing Corbel in West Gate Tunnel. ATC 2023. Design of the project is undertaken by Aurecon-Jacobs Joint Venture (AJJV) and construction is undertaken by CPB-John Holland JV (CPBJHJV)
Cut & Cover We also see more interest to consider hybrid solutions for Cut & Cover (C&C) tunnel construction. For such applications, the structural design would
be executed in accordance with the newly established Eurocode 2 Annex L, which provides a harmonised regulatory framework for the use of fibres in structural concrete. The primary design objective was to utilise steel fibres for SLS requirements, specifically for crack width control. By leveraging the post-cracking residual strength of the SFRC, the project team aimed to significantly reduce the density of traditional longitudinal and transverse rebars. Mock-ups developed in Belgium for the Antwerp Channel
Tunnels, and in Singapore under the supervision of the Construction Technology Innovation Laboratory (CTIL) and the Singapore Institute of Technology, are very promising. They confirm the feasibility of, and future opportunities enabled by, high-performance steel fibre.
Caverns We also see that FRC could support better use of underground space in a proposal for larger, deeper excavations. The ECO Caverne concept is being developed by Swiss startup ECCUS as an innovative but standardized underground infrastructure solution that would enable industrial operators, data centres, energy companies, and real estate developers to increase their usable space while preserving surface land. Three standardised sizes of caverns are envisaged to meet different project requirements. The approach would be to build a cavern project under a fast- track turnkey contract, made possible by the absence of any permanent surface structure. By constructing standardised underground caverns, ECCUS could help organisations to overcome land scarcity, reduce environmental impact, and improve the sustainability of their operations. A key differentiator of the ECCUS ECO Caverne concept
is the use of a permanent sprayed dry concrete lining as the primary structural support system. The permanent FRC sprayed concrete lining is a critical enabling technology for the solution. It provides permanent ground support immediately following excavation, allowing efficient construction in a wide range of geological conditions. Following an intensive testing campaign to optimise the
sprayed concrete recipe and application process, ECCUS is expected to deliver its first ECO Caverne project soon.
18 | October 2026
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