Study On Bond Performance Of Anchor Rod Under Dynamic Load And Corrosion

As an effective support and reinforcement measure,rock-soil anchoring technology is widely used in the construction of various engineering projects.Since the natural environment and stress states of the anchoring system are complex,the mechanical responses are different from usual.At present,the research on the mechanical mechanism of anchoring system under static load is abundant,but the research on durability and dynamic performance in complex environments such as corrosion and dynamic load is relatively weak.However,such complex environments put forward a challenge to the safety of anchoring projects.Therefore,it is of great practical significance to carry out research on the dynamic bonding properties of corroded anchor rods for the design of anchoring structures and the safety assessment of in-service anchoring systems.This paper is funded by 2018 Technology Talent Support Program Dalian Distinguished Youth(2018RJ10),and the dynamic bonding properties of corroded mortar anchor rods are explored.The main contents of the research are as follows.(1)The dynamic pull-out tests of corroded mortar anchor rod were designed and carried out.Given the characteristics of anchoring structure and the stress transferring along radial direction in practical engineering applications,the layered cylindrical anchor rod specimens were designed and produced.The surfaces of the steel bars were quickly rusted to simulate the corrosion state in a corrosive environment.The strain data of steel bars were collected by the strain gauges pasted inside the wire-electrode cutted steel bars.The MTS electro-hydraulic servo test system was adopted to control the loading frequency of the sinusoidal load,which simulated the dynamic stress states of anchor rods.(2)The anchoring performance of the anchor rod was studied according to the pull-out test results.Based on the measured strain data,the bond stress of of the steel bar-mortar interface was fitted by the matrix equation method.The load-slip curves and the curves of the strain and stress distribution were plotted to investigate the effects of the corrosion,corrosion location and loading frequency on the pull-out bearing capacity and interfacial bond performance of the anchor rod.The results showed that the presence of the rust had a great influence on the pull-out bearing capacity and bond performance of the anchor rod,where the bonding state of the front-part(loading end)anchor rod was the most critical to the overall anchorage quality.As the loading frequency increased,the pull-out bearing capacity gradually decreased,while the peak value of bond stress gradually increased,and the distance that bond stress transferred along the anchorage direction gradually decreased.(3)The physical pull-out tests were simulated by the finite element software ANSYS.The steel bar and the mortar were connected by the zero-thick surface-to-surface contact elements.The bond state between the steel bar and the mortar was simulated by adjusting the interfacial friction coefficient and initial bond stress.The calculation results of steel bar stress,interfacial contact pressure,and bond stress were analyzed.The results of finite element analysis showed that the results show that the corrosion location had a great influence on the interfacial contact pressure,and the distribution trend of the bond stress were overall consistent with the test results.Based on the reliability of the numerical simulation results,the parameter sensitivity study of the corroded mortar anchor rod was carried out,and the influence of the mortar layer thickness,the anchor length and the corrosion degree on the bonding properties of the anchorage interface was analyzed.