Effect of vehicle speed and overload on dynamic response of semi-rigid base asphalt pavement

Premature deterioration in semi-rigid base asphalt pavement is still considered as one of the main distress related to Chinese highway pavements. There are several reasons for this premature damage and these include poor design and construction, a sudden increase in traffic loading and the dynamic loading of overloaded heavy truck. This paper investigated the effect of vehicle speed and traffic overload on the dynamic response as well as on service life of a semi-rigid base asphalt pavement with typical functional requirements. The study involved simulating the critical stress–strain response at the bottom of asphalt layer under different load weight level and vehicle speed. A large scale three-dimensional viscoelastic finite element model of transient dynamic analysis of the pavement was developed. The Sinotruck HOWO-A7 6×4 and HOWO-A7 8×4 were selected as a representative heavy truck and the associated contact stress effect of each isolated wheel load on the pavement structure was incorporated in the implicit dynamic analysis by a developed DLOAD subroutine. Field dynamic strain measurement from Fiber Bragg Grating strain sensors at the Rizhan-LanKao G1511 highway test section was successfully used to validate the developed model. The results of this study indicate that under heavy moving truck load the response time of the longitudinal, vertical and shearing stress–strain at the bottom of the asphalt layer has both a tensile and compressive component, while the response time history of the transversal stress–strain has only a tensile component. The result also indicated that a decrease in the vehicle speed not only induce a significant increase in the load duration on the structure but also amplified the shock effect induced by the wheel load. The damage caused by the overload is greatly influenced by the axle weight extra extent. The fatigue analysis results revealed that, factors such as overloading or low-speed traffic could result in adverse effect on the service life of pavement. However, as expected the tensile strain at the bottom of the asphalt layer of the proposed semi-rigid base asphalt pavement structure is less than the critical strain of a conventional pavement structure with an ordinary asphalt mix even under critical conditions such as overloading or low-speed traffic.