This research provides a theoretical method for the design of a full column bolt with bottom plate. When using full column bolts with plates the initial anchorage forces exerted by the plate depend on the rock strength and construction time. In order to estimate quantitatively the mechanical action of the plate and to evaluate the support effect of the initial anchorage forces, mechanism and calculation methods for bolts with bottom plate and initial anchorage forces for weak and hard rocks were carried out. Based on the failure model of the bottom plate a formula for calculating plate failure is given. Finally, the mechanism and computing methods for bolting and shotcreting with a steep reinforced strip in unstable rock were studied.