Research On Dynamic Response Of Asphalt Pavement Based On Full-scale Accelerated Loading Test

The current asphalt pavement design specifications and mechanical analysis methods in China are based on the theory of laminar elasticity under the static vehicle load effect,and do not consider the overload,vehicle speed,viscoelastic properties of the asphalt mixture,and the dynamic properties induced by the vehicle load.Therefore,there is a gap between this design theory and the real mechanical response of the pavement structure caused by the dynamic vehicle loads in real situations.In this thesis,we try to analyze the change law of the internal mechanical response index and the response time curve characteristics of the pavement structure under the action of MTS vertical impulse load through the accelerated loading test of the lane level full-scale pavement structure;monitor the road surface deflection value of different pavement structures under different loads based on FWD and self-developed road surface deflection test system;establish the three-dimensional model of the footprint accelerated loading test road by using finite element software to study the dynamic response of the pavement structure under different loads.The three-dimensional model of the pavement structure of the test road was established by using the finite element software to study the changes of the internal strain of the pavement structure and the changes of the road surface deflection under different working conditions.The main research contents and results are as follows.(1)By investigating the typical pavement structures of highways in Shandong Province at different stages,combined with the accelerated loading test tank size,the full-scale test road was set into four different pavement structures,and the bottom strains of different pavement structure layers and the road surface deflection settlement values were taken as monitoring indicators to study the dynamic response law.The results show that the strains at the bottom of the layers of different pavement structures are sensitive to the changes of the loading action,and the periodicity of the results is relatively stable,and the time course curves of the strain response at the bottom of the layers are basically the same under the action of the same loading frequency.(2)The measured deflection and settling basin curves by FWD and MTS both decrease with the increase of radial distance and increase with the increase of load level.The influence range of the deflection basin of the same pavement structure under different load levels does not change much in general.By calculating the ratio between the actual load and the deflection basin at each point under the action of FWD,it can be seen that with the increase of the distance from the load center,the deflection ratio at each measurement point roughly tends to increase first and then decrease,and the change of the load multiplier is not equal to the change of the deflection multiplier,which reflects the nonlinear characteristics of the pavement material under the action of impact load.By analyzing the deflection and sinkage data measured by laser displacement sensors at different positions under the action of MTS,it can be seen that with the increase of load frequency,the time of reaching the peak deflection and sinkage of each sensor gradually decreases,and the deflection and sinkage values measured by sensors at the same position do not change with the change of frequency;the deflection and sinkage values at each point decrease with the increase of horizontal distance of sensors from the center of the load;the time of reaching the peak of each sensor under the action of the same frequency is different,and there is a certain hysteresis.There is a certain hysteresis.(3)The strain response model of asphalt pavement was established based on the measured response data,and the linear analysis of the calculated strain and the measured strain showed that the calculated strain calculated by the strain response model had a high correlation with the measured strain;by calculating the pavement deflection basin area index(AUPP)and combining the measured response data,a prediction model was established between the pavement deflection basin area index(AUPP)and the deflection tensile strain of the surface layer subgrade.By calculating the AUPP and combining the measured response data,a prediction model was established between the pavement deflection basin area index(AUPP)and the surface layer bottom deflection tension strain.(4)Based on the finite element software and the measured material parameters,the finite element model of the accelerated loaded test road under static and dynamic loads was established,and the simulated structure was compared with the measured response data,and the deviation of the measured layer bottom tensile strain and road surface deflection settlement values of different pavement structures from the calculated values was less than 20%.The validity of ABAQUS calculation results in the calculation of structural mechanics of asphalt pavement is verified by comparing the calculated and measured values.