Engineers Australia

A Review Of The Behaviour Of Domed Rock Bolts Plates And Their Use In Sydney Tunnelling

D A F Oliveira and P Kozak

Abstract

The design and construction of semi flat-roofed tunnels in hard rock often involves the use of thin shotcrete linings that have the main function of supporting minor wedges which can form between rock bolts. The rock bolts perform a dual function in the tunnel support system: they improve load bearing characteristic of the rock mass and provide support to the shotcrete spanning between them. This paper focuses on the latter purpose and demonstrates that caution needs to be exercised when designing rock bolt plates for the tunnel support application where rock bolt plates are installed prior to shotcrete, i.e. directly against the rock surface. While the load transfer mechanism through punching shear is a well-studied mechanism for rock bolt plates installed against the surface of shotcrete lining, i.e. the intrados, the transfer mechanism for the plates installed inside the shotcrete is less researched and understood as it is more complex and is not widely used across the world. Laboratory and in-situ testing as well as advanced FEM analyses aimed at providing guidance on the expected load bearing capacity are presented in this paper.