Effect of profile bolt in bond strength fully grouted rock bolts using analytical and experimental methods

Abstract

Steel rock bolts are widely used in mining and tunnelling engineering to support underground excavation or to stabilise a rock mass. The anchorage capacity of fully grouted bolts has been studied for many years; however, the fully grouted rock bolts and its effect is poorly understood. A new analytical approach able to predict the bond strength of fully grouted rock bolts is proposed in this paper. Input parameters are: rib profile shape, height, width, angle of wrap and spacing, axial bolt pull-out force, material properties. As for the analytical part, the basis of the new analytical solution for the prediction of the load-displacement curve was developed. Derived mathematical equations enable calculations of grout displacement in elastic and elasto-plastic behaviour. In the experimental part, six bolts in situ pull-out tested were compared with the predictions of the new analytical approach and this comparison led to the validation of this approach.