Evaluation of the Amount of Deflection Recovery by Stratified Repair Using a Hidden Markov Deterioration Model

In Japanese expressway pavements, deeper layers are damaged due to the change of surface layer material from dense-graded pavements to high-performance pavements and the decline of structural load-bearing capacity caused by deterioration. In practice, stratified repair is conducted depending on the state of damage, and therefore, road managers need to determine the most suitable repair layer while simultaneously considering repairing damage and reducing construction costs and economic loss due to traffic restrictions. For that purpose, it is necessary to quantitatively evaluate how much the structural load-bearing capacity has been restored by the stratified repair and clarify the relationship between the effect of the stratified repair and the structural load-bearing capacity. In this study, the authors attempt statistical modeling of the state of structural road-bearing capacity. Specifically, the authors propose a hidden Markov deterioration model for expressway pavements that describes the transition of the load-bearing capacity of the pavement structure with a combined process, which consists of (1) a process of deterioration with age and (2) a process of recovery through repair. With this, it is possible to not only predict the decline in structural load-bearing capacity, but also quantitatively evaluate the degree of recovery at the time of repair as a transition probability. Furthermore, the authors conduct an empirical analysis of the proposed model based on the load-bearing capacity evaluation by FWD (Falling Weight Deflectometer) data conducted on the expressway and discuss the usefulness of the model.