Research On Mechanical Behaviors And Bearing Characterictics Of Fully Grouted Anchorage System

With the gradual complexity of the geological conditions of coal mining in China,a large number of complex and difficult roadways have gradually appeared,which has brought troubles to the safe and efficient production of coal mines.The fully grouted anchorage system is an important part of bolt support,and a better understanding of its mechanical behaviors and bearing characteristics is of great significance to the surrounding rock control of complex and difficult roadways.Based on the investigation and summary of the current research status,the mechanical behaviors and bearing characteristics of the fully grouted anchorage system were systematically studied by means of experimental exploration,theoretical analysis and numerical simulation in this paper.The main conclusions are as follows:(1)The bearing characteristics of the anchorage system were studied,the mechanical properties,strain characteristics and acoustic emission responses of the anchoring interface were systematically analyzed.The bearing mechanism and failure characteristics of the anchoring interface were clarified,the bond-slip relationship of the anchoring interface was obtained and the evolution characteristics of the bond strength of the anchoring interface were described by using the cap strength model.(2)A mechanical model of the thick-walled circular ring of the anchorage system was established,the mechanical bearing mechanism of the anchoring interface was analyzed and the governing equation of the bonding strength of the anchoring interface was obtained.The influence of the mechanical properties of the anchorage medium and the diatancy effect of the interface on the bonding strength of the anchoring interface was investigated and the key factor affecting the bonding strength of the anchoring interface was determined.According to the mechanical bearing mechanism of the anchoring interface,a method of adopting steel fiber anchorage agent to enhance the bearing performance of the anchorage system was proposed,the performance enhancement mechanism of the steel fiber anchorage agent was discussed and the performance enhancement effect of the steel fiber anchorage agent was verified through experiments.(3)The mechanical response characteristics of the anchorage system under different loading rates were investigated.The effects of loading rates on the bearing performance,acoustic emission responses and failure characteristics of the anchoring interface was systematically analyzed.The internal influence mechanism of the loading rate on the bearing characteristics of the anchoring interface was clarified from a theoretical perspective.Moreover,a method of using acoustic emission counts to evaluate the damage and failure characteristics of the anchoring interface was proposed and the expression of the damage parameter of the anchoring interface was obtained.The theoretical analysis results were in good agreement with the experimental results.(4)The progressive failure characteristics of the anchorage system under the pull-out action were analyzed,and the analytical solutions of the load-displacement,axial force and shear stress of the bolt in each bearing stage was obtained.The rationality of the theoretical analysis was verified by using numerical simulations.The pull-out bearing process and force evolution characteristics of bolt with different anchoring lengths were explored,and the influence of anchoring length of bolt on the bearing characteristics was revealed.(5)Considering the strain softening characteristics of the surrounding rock deformation of the roadway,a mechanical model of bolt-surrounding rock interaction was established,the analytical solutions of the axial force and shear stress of the fully grouted bolts in different surrounding rock conditions were obtained and the influence of rock stress,rock expansion coefficient,rock softening modulus and axial force of bolt end on the force characteristics of fully grouted bolts was explored.Moreover,a numerical realization method of prestressed fully grouted bolt support was proposed,the rationality of the theoretical analysis was verified by numerical analysis,and the influence of rock type,bolt pre-tightening force and bonding stiffness of anchoring interface on the force characteristics of fully grouted bolts was further studied.