Experimental study on bolt pull-out property coupled by plate and shotcrete

Abstract

Based on a self-developed multi-function bolt mechanical test system, axial pull-out loads were applied on same bolts under the different conditions, combining with flat plate, butterfly plate, new-type plate and three kinds of shotcrete(C15, C20 and C25 plain concrete). Experimental results showed that the relationship between bolt elongation and drawing force has three stages, including elastic, yielding and strengthening. The strength of shotcrete lining has obvious influence on the bolt stiffness during the elastic stage i.e. the strengthening of the concrete leads to the increase of bolt stiffness. The strength and width of the yield platform of the bolt reach the maximum for butterfly plate and yield plate with C20 plain concrete lining. Butterfly plate and new-type plate both have yield functions, and the latter one can effectively prevent the damage of shotcrete. The damage of shotcrete lining usually begins around of drill holes, when the interfacial stress between the initial shotcrete lining and surround rock is higher than that in the initial lining and secondary lining. With the new-type plate used, the cracks in the secondary lining cut through along the same direction.