Study On The Load-bearing Mechanism Of Tunnel Composite Support Structure Considering Interface Slip

With the rapid development of China’s economy and the expansion of the scale of transportation infrastructure construction,more and more tunnel projects are built in various complex conditions areas.In the actual tunnel project,the impact of the pressure of the surrounding rock,by the cracking of the shotcrete,and then caused by the steel-mixed interface slip damage,and finally caused by the composite support structure damage is a form of support structure damage.The damage of the composite support structure caused by the slip of the steelmixed interface is mainly caused by the slip of the interface between the steel and concrete,and the natural bond between the steel and concrete in the composite support structure is the basis for ensuring that the steel and concrete work together as a whole in the composite support system.Therefore,it is of great scientific significance and technical application value to consider the influence of interfacial slip on the bearing capacity of composite support structure,to carry out research on the bearing characteristics of interfacial slip on composite support structure,to reveal the mechanism of interfacial slip of steel and concrete,and to clarify the bearing mechanism of composite support structure considering interfacial slip.In this thesis,the bearing mechanism and damage mechanism of tunnel composite support structure under the consideration of interface slip are investigated by means of steel-concrete roll-out test,indoor bearing test of composite support structure and numerical simulation,and the influence of interface slip is taken into account in Shantou Bay undersea tunnel as the engineering background,and the support design parameters are optimization is carried out.It is mainly divided into the following contents:(1)Carry out profile concrete push-out experiment,according to the test phenomenon,analyze each specimen surface crack category and development law,by summarizing the loadslip curve of profile concrete push-out specimen,get a simplified interface slip characteristic curve model,clarify the development of the bonding action of the contact interface between profile steel and concrete at each stage of the loading end curve,based on the interface slip characteristic curve model,calculate the profile concrete characteristic value.And based on the launch test,ABAQUS finite element numerical simulation analysis is carried out to construct the numerical analysis model of the section concrete specimen,and the numerical analysis results are compared and analyzed with the test results to verify the reasonableness of the numerical model of the section concrete launch specimen.(2)Using the numerical modeling method of profile concrete launch specimen to construct the finite element model of composite support structure with and without considering interface slip,analyze the mechanical properties of composite support structure under the influence of interface slip and the stress-strain and development law of related materials.By carrying out research on the bearing mechanism of composite support structure,different parameters(arch spacing,longitudinal connection bar diameter,longitudinal connection bar ring distance and concrete strength)are studied on the bearing mechanism of composite support structure.Based on gray correlation theory,the correlation between different parameters and the ultimate bearing capacity of the composite support structure is analyzed.Compare and analyze the ultimate bearing capacity of the composite support structure with or without considering the interface slip,and define the discount rate of the bearing capacity of the composite support structure.(3)Carry out indoor bearing test of composite support structure,analyze the test phenomenon during loading and the crack development law.By summarizing the loaddisplacement curves of the composite support structure specimens,a simplified load-bearing characteristic curve model of the composite support structure is obtained,and the mechanical characteristics of each phase of the composite support structure are clarified.By analyzing the influence law of arch spacing and steel fiber on the bearing capacity of composite support structure,the mechanism of the effect of steel fiber on the bearing mechanism of composite support structure is clarified.Finally,the test results under different arch spacing are compared and analyzed with the numerical analysis results to verify the correctness of the bearing action mechanism of the composite support structure.(4)Taking Shantou Bay undersea tunnel as the engineering background,the numerical simulation study on the control of surrounding rock deformation of composite support structure is carried out considering the influence of interface slip of composite support structure.By analyzing the surrounding rock deformation,surrounding rock stress,surrounding rock plastic zone and support structure stress,the original tunnel support design parameters are optimized,and the influence law of different arch spacing,longitudinal connection bar diameter and concrete strength on the displacement of the surrounding rock vault is analyzed to obtain the optimal support design parameters.