Study On Influence Of FWD Caused By Adjacent Overload

With the gradual improvement of infrastructure of construction in China,the number of highway maintenance works will rise significantly.At the same time,because of the regional economic and the increasing traffic,there is less time for the capital repair project of pavement.The later completion detection will also be affected.In the deflection detection of asphalt pavement,with the promotion of Falling Weight Deflectometer,the asphalt pavement deflection detection is automatic.In order to cooperate with the construction period,people have used Falling Weight Deflectometer to test asphalt pavement under the condition of open traffic.In practice,the asphalt mixture is affected by complex external factors.In the case of open traffic,it is necessary to explore the influence of the moving load of adjacent vehicles on the detection.In order to reflect the viscoelasticity of asphalt mixture,the dynamic modulus of asphalt mixture is used for the dynamic response analysis of asphalt pavement by ANSYS.According to the influence factors of dynamic modulus,the temperature distribution of pavement and the load or speed of vehicle is discussed in this paper.The pavement temperature distribution is determined by the existing prediction model of asphalt pavement.The vehicle driving load is determined by the force analysis of the 1/4 model of vehicle,using the vehicle load and the vehicle speed.Because of restrictions on test conditions,the dynamic modulus of asphalt mixture is determined by the prediction model of dynamic modulus,using the gradation and volume parameters which gotten by test.Besides,the base course is simulated by linear elastic model and the soil base is simulated by elastic-plastic model.After comparing the test data and simulation data,the influence of asphalt pavement deflection detection is analyzed by using the reliable finite element model and control variable method.After the simulation analysis of three factors,it is not difficult to find that the dynamic response of asphalt mixture is the result of viscous hysteresis and elastic recovery.In the process of mechanical response,the displacement of pavement points is a function of time in a certain range.There is more vertical displacement of the pavement near the load action center when the vehicle load increases.Besides,the rest of the pavement is also uplifted more.When the vehicle speed increases,the dynamic modulus of asphalt mixture and the dynamic coefficient of cars are changed.So the accurate law is difficult to be found.When the pavement temperature increases,the viscosity of asphalt mixture is more prominent.The displacement of pavement is a little later than the load.In summary,according to the finite element simulation results,the dynamic deflection detection using Falling weight Deflectometer is not recommended under the condition of open traffic,especially heavy haul freight traffic.However,considering the actual work,the detection test should be done in a low temperature and low speed of adjacent vehicles.