Use of Carbon Fibre Reinforced Polymer (CFRP) as an alternative material in permanent ground anchors Matthew Sentry 1,2 , Abdelmalek Bouazza 2 , Riadh Al-Mahaidi 3 , Darren Loidl 4 , Chris Bluff 5 , Len Carrigan 6 1, 2, 3 Department of Civil Engineering, Building 60, Monash University, VIC, 3800, Australia 1, 4, 5, 6 Geotechnical Engineering, 68 Springbank St, Tullamarine, VIC, 3043 Australia ABSTRACT Steel tendon ground anchors are an integral construction technique for numerous civil engineering applications ranging from deep excavation support to resistance of structural uplift and overturning of superstructures. Failures of steel strand ground anchor systems are rare, but when they occur, corrosion and human error are the primary reason. Several methods of minimising anchor system corrosion have been adopted over time to minimise ingress of corrosive substances. However, anchors are still failing due to corrosion. Advancement in the development of corrosion resistant materials has been at the forefront of materials research. In this respect, research and development of FRP materials is enabling the progress of providing the industry with a more potentially robust anchor system aimed at eliminating current limitations encountered with steel strand ground anchors. This paper provides an overview of current best practices for the application of permanent ground anchors and investigates the current developments in FRP materials for ground anchor applications as an alternative to conventional steel tendon ground anchors. The paper also provides insight into known areas where further research is required to assist the introduction of FRP ground anchors into standards. 1. INTRODUCTION AND BACKGROUND Ground anchors can be classified as a substructural members that transmits a tensile force from the main structure to the surrounding ground (Hanna, 1982). Ground anchors are used in a variety of civil engineering applications to stabilize rock/soil faces and resist uplift and overturning forces acting on structures (Littlejohn and Bruce, 1977; Weerasinghe and Adams, 1997; Xanthakos, 1991). With the exception of the development of the single-bore-multi-strand ground anchor system developed by Tony Barley (Barley, 1995, 1997), ground anchor design has not changed dramatically since the works carried out by Littlejohn and Bruce (1977) and Hanna (1982). Current international ground anchor standards and guidelines (EN, 2000; RTA, 1999; Standards, 2002) refer only to the use of the well established stressed relieved steel strand system (Sentry et al., 2007a). Although these permanent ground anchor systems utilise the rugged steel tendons with readily available hardware for anchor applications, they are still vulnerable to corrosive attack from aggressive environments. Recent research has focused on improvements to anchor corrosion protection. Current permanent ground anchor standards require the use of double corrosion protection systems encapsulating the steel strands, to ensure a serviceable design life (Sentry et al., 2007b). Technological advancements of fibre reinforced polymers (FRP) for applications in civil construction has allowed new products such as glass fibre (GFRP), aramid fibre (AFRP) and carbon fibre (CFRP) to pave the way for research into further improvements to the currently favoured steel strand ground anchor system. FRP’s are characterised by their perceived superior resistance to aggressive ground environments, compared to steel. Where steel reinforcement has been restricted due to aggressive ground conditions, minimal alternatives have been available for industry use until FRP reinforcement was developed and successfully used as a durable construction alternative. Extensive research has been conducted on FRP as a substitute for conventional steel reinforcement; however there is minimal knowledge on FRP limitations, especially its behaviour over prolonged exposure to aggressive ground environments. 2. GROUND ANCHOR LIMITATIONS In recent times, 35 known cases where permanent ground anchors were identified as having failed during their design lives due to corrosion related failures of the steel strands (Littlejohn, 1987; Littlejohn and Mothersille, 2008a, b). The report