The conventional tunneling methods (i.e. drill & blast tunneling method or New Austrian Tunneling Method) have been frequently applied for the construction of tunnels/caverns under a high overburden or extremely shallow cover with a large cross section. Under such adverse conditions, the tunnel support materials may yield due to ground pressure and tunnel deformation. As a result, the tunnel may lose its stability due to reduced effectiveness of the tunnel supports.
Rock bolt has been widely used as one of the essential tunnel supports, and many studied have been carried out on the performance of rock bolt in strengthening the jointed rock mass. However, there is a lack of understanding on the interface behaviour between the rock bolt and bond material, especially the crack initiation and propagation inside the bond material. This study aims to investigate the interface behaviour between the rock bolt and bond materials using laboratory tests (shear tests) and numerical simulations (discontinuous deformation analysis). By assessing the impact of the key parameters in the rock bolting system, we are able to better understand the supporting mechanism and the effects of rock bolting in detail.
The work presented here includes both experimental tests and numerical simulations on the interface behaviour between the rock bolt and bond material. It is well known that rock bolts are the essential supports for rock tunnels and large rock caverns. There have been many studies on the rock bolting system to understand their effects and reinforcing mechanism (Farmer 1975, Goodman 1989, Aydan 1989, Hyett et al. 1992, Yazici & Kaizer 1992, Li & Stillborg 1999, Obara et al. 2002, Kilic et al. 2003, Aziz et al. 2008 and Cao 2012). Though many researches have been conducted to understand the reinforcement mechanism of rock bolts, there is still a lack of understanding on the interface behaviour between the rock bolt and bond material, especially on the crack initiation and propagation into the bond material. Moreover, no research has been conducted to evaluate these cracks using numerical methods which can simulate the crack initiation and penetration into the bond material. The purpose of this study is to analyse the influence of one key parameter in the rock bolt system, mortar strength, on the mortar failure patterns and reinforcing effect using shear tests and to develop numerical models to simulate the crack behaviour and to reproduce the result of shear tests. This study on the interface behaviour will enable us to better understand the supporting mechanism and effects of rock bolting in detail, so as to better design the rock bolting system.
