Mechanical Characteristics Of Rock Bolt Anchoring System Under Dynamic-static Coupling Loading

The rock bolt is the basic member in geotechnical engineering.Dynamic disturbances induced by rock burst and blasting,etc.,will bring damages to the supports of the deep rock and soil anchoring.Such dynamic damages are essentially caused by these dynamic responses associated with the rock pressure.Therefore,these damages are the results of dynamic-static coupling loading.And thus,the mechanical characteristics of the rock bolt anchoring system under dynamic-static coupling loading is a fundamental problem for the stability control of the deep rock and soil anchoring.By experimental investigations,the failure process and failure modes of the rock bolt anchoring system under dynamic-static coupling loading is study in this paper.Based on the finite element software,bond stress distribution in spatial and temporal expression,bond-slip behaviors and the influences of initial stress state of surrounding rock,initial static load level and anchorage length,etc.on them.The failure mechanism will be explored and bond-slip model will be developed.The specific studying context includes the following aspects:(1)Based on the laboratory tests,the bearing capacity changing law and the failure mode of the rock bolt anchoring system under static loading,dynamic loading and dynamic-static coupling loading are studied to analyze the differences,relations and functional mechanism of the rock bolt anchoring system.Test results show that the failure modes of the rock bolt anchoring system under above-mentioned conditions are the interface debonding failure of the anchor and grouting body;whereless,the ultimate bearing capacity of the rock bolt anchoring system shows different under different condition: minimum under dynamic loading,maximum under dynamic-static coupling loading and median under static loading.(2)Based on the finite element software,the stress distribution law of the interface between the anchor and the grout interface is simulated in condition of initial static load,stress of surrounding rock and anchorage length.The results show that with the increase of initial static load level,the interface bond stress transmits further to anchor free end;surrounding rock stress can affect the distribution of interface bond stress only under little added loading;the free end of rock bond system shows no bond stress when the anchorage length excesses a certain value.(3)Based on the damage theory,through the analysis of the test results and the simulation results,bond slip relationship of the rock bolt anchoring system was prosed under dynamic-static coupling loading.In the initial stage of the cycle,with the increase of the number of cycles,the cyclic variable is increasing and the damage of the anchor is constantly damaged;while in the later period of the cycle,the cyclic variable tends to be stable and the anchor has reached the final failure state.