A Study On Dynamic Response For Half Rigid Pavement Structure

The traditional theory about the design of Asphalt Pavement, treat the vehicle load as static in road design, and ignore the basic characteristic of load. It is reasonable when the vehicle load is small and speed is very low. however, because of the improvement of the quality of asphalt, the speed of vehicle increased largely, the difference between static load and real interaction force of running vehicle is significant, and the road dynamic characteristic can not be described with static characteristic. So, it was necessary for trying to simulate the pavement dynamic response to the running vehicle.Dynamic loading caused by the actual running vehicle was a random load, not only the size was changed, but also location was changed too. So it is difficulty to actually simulate the random load. The former research has predigested the two characteristic of load (one is dynamic, the other is moving), just choused one of the characteristic to research.In this paper, the three-dimensional (3D) finite element dynamic method was adopted. Consider the two characteristic of the dynamic load; this load was simplified as fluctuating load and moving load. Simulated and computed the dynamic response of the half rigidity road of different vehicle speed and vehicle load, and anglicized the affection to the traditional design index.The simulation results indicated that the fatigue cracking was caused by the combined action of horizontal stress, transverse stress and vertical stress of the dynamic vehicle load, and the alternate horizontal stress was the main factor of all , and the action of transverse was also can not be ignored. The crab of asphalt concrete was mainly because of a great deal of shear strain; horizontal direction and transverse direction of half rigidity base and half rigidity sub-base mostly was stretched. The maximum horizontal tensile stress and the maximum transverse tensile occurred at bottom of the half rigid sub-base, the fatigue cracking of the half rigidity road occurred at the half rigid sub-base firstly. The horizontal shear stress and transverse shear stress caused by the interact action of vehicle and road had large influence to the shear stress of asphalt concrete, and had no influence to the flexure of the half rigidity road, what's more, mostly had no influence to the fatigue break-down caused by bend and stretch. However the outcome of this two simulate method were completely inverse in some indexes.