A laboratory and field research programme was conducted to investigate the major factors influencing the bond capacity of grouted cable bolts. All tests were conducted on standard 5/8" (15.9 mm) 7-strand cable grouted using type 10 Portland cement pastes. The results indicate that cable bolt capacity most critically depends on: (i) the cement properties, which are primarily controlled by water : cement ratio; (ii) the embedment length; and (iii) the radial confinement acting on the outer surface of the cement annulus. The material properties of cement paste vary with the water : cement ratio of the mix. The use of low water : cement ratio grouts (< 0.40 by wt) can increase peak cable bolt capacities by 50-75%. This can be attributed to both their high uniaxial compressive strengths and their high Young's moduli. The effect is maximized under conditions of high radial confinement. However, the use of super -thick pastes (0. 30 and less) may be both impractical and undesirable, first because of their limited pumpability and second because of their inconsistency in strength. Tests at different embedment lengths indicated that cable bolt capacity increased with embedment length although not in direct proportionality. All tests were conducted with embedment length: cable diameter ratios in excess of 15 (below 5 the decay in shear stress along the cable can be ignored). Consequently, failure is non-simultaneous in nature, with one section having failed while another is approaching peak capacity. In the laboratory "split-pipe " tests were conducted using PVC, Al and steel pipes to provide radial confinement, and in the field, surface test sites were chosen in granite, limestone and shale rock masses, as well as an underground case study at the Golden Giant Mine. In general, higher capacities were obtained under conditions of higher ra&al confinement. A correlation between the laboratory and the field test results was obtained through a comparison of the radial stiffness of the laboratory pipes with that of the field boreholes as measured using a high-pressure dilatometer. As the degree of radial confinement increased the failure mechanism changed from radial fracturing and lateral displacement of the grout annulus under low confinement, to shear of the cement flutes and pull out along a cylindrical frictional surface under high confinement.
