Alun H. Thomas, BA, PhD, CEng, MICE



Traditionally steel has been used for rock bolts in tunnelling. Faced with the challenge of reducing mankind’s environmental impact, it is necessary to look at using better alternatives.

Glass-fibre-reinforced polymer (GFRP) has been used for many years in tunnelling applications, primarily for temporary applications. GFRP has many advantages such as its excellent durability characteristics, its light weight, which reduces manual handling impacts on workers in the tunnel, and its lower environmental impact.

One obstacle to the more widespread adoption of GFRP for permanent applications has been a concern over its performance in shear. It is well understood that during shearing the rock bolts actually deform under bending and the tensile strength of the bolt governs the behaviour.

This paper will describe a new design method to account for the benefit of the bolts in resisting shearing on discontinuity planes. This method can be used in numerical models to demonstrate that GFRP bolts function as well as steel bolts in terms of resisting both tensile and shear loading from the rock mass.

This opens the path for the wider use of GFRP rock bolts, which offer superior durability and a lower environmental impact.


geotechnical engineering tunnels & tunnelling sustainability