Variation of anchoring force during the course of deformation and failure of surrounding rock

True triaxial experimental bench is creatively used to carry out bolting experiments on a large scale of 1:4,the whole course from excavation to failure of surrounding rock is found out ,that is,dilatancy deformation stage of rock within bolting range, dilatancy deformation stage of rock beyond bolting range,and rock failure stage. Variation law of anchoring force is grasped respectively during each stage,which is the scientific basis of bolting design.The rapid decrease of load on bolts may be used as an index to forecast the destabilization of surrounding rock.