Study On Structural Response Of Asphalt Pavement With Flexible Base Of Tunnel

At present,the dynamic design of pavement structure is one of the hottest topics in the field of road research.However,there are few researches on tunnel pavement structure by researchers.Therefore,this paper studied the mechanical response law of tunnel flexible base asphalt pavement structure under moving load through the combination of full-scale pavement acceleration loading test and numerical simulation,and explores the dynamic principle of tunnel flexible base asphalt pavement.The research results can provide some data and theoretical support for tunnel pavement design.First,the strain and temperature data at the bottom of the asphalt mixture layer were collected through the accelerated loading test of the flexible base asphalt pavement of the full-scale tunnel.At the same time,the vertical compressive stress and temperature data at the bottom and top of the graded gravel layer were collected to study the asphalt mixture.The changes of the strain at the bottom of the material layer along the traveling direction during the instantaneous,daily loading process and the loading process of 1 million times,and the different changes in the stress of the top and bottom of the graded crushed rock layer during the loading process are compared and analyzed.The research shows that: in the process of one movement of wheel load,the horizontal strain response of the bottom of the asphalt mixture layer along the direction of the vehicle is divided into three stages.The first stage is that before the wheel reaches the response point,the response point is subjected to compressive stress,resulting in compressive strain;the second stage is that the wheel reaches above the response point and before leaving the response point,the response point stress rapidly changes from compressive stress to tensile stress,and When the wheel is directly above the response point,the tensile stress is the largest,and the tensile strain is also the largest at this time;the third stage is that after the wheel leaves the response point,the response point continues to be subjected to compressive stress,resulting in compressive strain.When the wheel is far enough away,the stress and The strain tends to zero.Under the action of moving load,the strain at the bottom of the asphalt mixture layer along the traffic direction is greater than the transverse strain;the instantaneous strain at the bottom of the asphalt mixture layer on the tunnel pavement along the traffic direction alternates between tensile strain and compressive strain,and the maximum strain is tensile strain.Then use the 3D-Move Analysis software to establish a three-dimensional finite layer model of the flexible base asphalt pavement of the tunnel.By comparing the calculation results of the finite layer simulation with the measured results of the fullscale test,the rationality of the finite layer model is verified and the moving load is explained.Under the action of the dynamic principles and laws of the bottom of the asphalt mixture layer along the direction of travel,the difference in the mechanical response of the asphalt pavement structure with the flexible base layer inside and outside the tunnel is also compared and analyzed.The research shows that the strain along the traffic direction at the bottom of the asphalt mixture layer of the flexible base asphalt pavement of the tunnel is smaller than that of the ordinary flexible base asphalt pavement;the vertical compressive strain of the top surface of the bedrock of the road in the tunnel is much smaller than the vertical compressive strain of the top surface of the ordinary road subgrade,The vertical compressive strain of the top surface of the bedrock of the road in the tunnel can be ignored.Finally,the influence of driving speed,asphalt surface thickness,and asphalt surface temperature on the mechanics response law of tunnel flexible pavement is studied.The research results show that under the action of moving load,traveling speed,surface layer thickness and surface layer temperature have no significant influence on the change trend of the bottom stress and strain of the asphalt pavement of the flexible base of the tunnel,but only have a greater impact on the value of the stress and strain.Increasing the driving speed,increasing the thickness of the surface layer,and reducing the temperature of the road surface can all reduce the strain value of the bottom of the road asphalt mixture layer along the driving direction and the vertical direction.