Twenty years of FRC tunnel final lining: Lessons learnt, design proposal and new development

New guideline concerning the use of FRC precast segment has been recently published to provide detail state of the art (ACI, FIB, ITA) and design proposal based on Model Code 2010. This paper will provide an overview of the lessons learnt and proposed design principle. The behaviour of fibre reinforced concrete is more than a simple superposition of the characteristics of the concrete matrix and the fibres. A unique concept of fibre has been developed which combined: high tensile strength + perfect anchorage (double hook) + ductile wire. This unique post cracking behaviour has been used to design very innovative solution. Three projects will be presented in this paper: the inner lining of Lee Tunnel in UK submit to internal pressure, the Jansen Mine shaft in Canada where shaft walls are slip formed and CIP tunnel in Turkey. All the design approach has been supported by a specific testing program.