Study on the Modeling Method Suitable for Pavement Rutting

Abstract

A paved road surface is in contact with a vehicle directly through its tire therefore its condition is closely associated with vehicle running 1) . It also greatly affects road user’s ride quality, safety and the living environment of roadside resident. Therefore, it is important to keeping track of the conditions and evaluate the conditions of the paved road surface, then make the suitable maintenance at the appropriate time according to the evaluation 2) . A major distress mode of the paved road is caused by road surface characteristics, such as rutting (pavement rutting), roughness and crack. Rutting and roughness are a special concern because these will affect road user and roadside resident directly. A longitudinal profile such as roughness has associated with elements which are related to the road user’s rating 3) . On the other hand, for the problems of a transverse profile such as the rutting, although there are the attempts being made to evaluate the rutting which affects the vehicle stability and controllability 3) , it has not yet reached to establish the evaluation index with the road user’s point of view. In Japan today, rut depth as an index for maintenance of the rutting has some disadvantages 2) . For instance, the index has problems the measurement method and definition of the rut depth differs from one administrator to another and it is does not reflect the road user’s point of view. There are two experimental approaches to estimate the road profile which affects vehicle behavior and road users. One approach is to use the actual vehicle with real road conditions. And the other is to use the simulation based on the vehicle dynamics (vehicle dynamics simulation). Recently vehicle dynamics simulation have developed and its achievements have become a center of attraction because it can do experiments to diagnose the road profile safely, rapidly and efficiently with same driving situation 3)-6) . The experiment for the rutting evaluation with the simulation has studied to concentrate on the vehicle dynamics 3) . However, the rut shape which is the object of investigation, especially the rutting caused by flowing which depends on heavy traffic, did not take into account the actual shape at the existing road, although it approximated only depression in the wheel path. Against this background, for the purpose of quantitative grasp of the rut shape, we developed the geometrical models of the rutting (the pavement rutting models) which simplified and approximated by use of comparatively easy functions and which have a moderate flexibility. The developed models were verified in respect of the adaptability of these shapes for actual road profile data and the applicability for the simulation method of the vehicle dynamics. The actual road profile is using part of the data which is obtained from the second Permanent International Association of Road Congress – World Road Association (PIARC) International Experiment to Harmonize Longitudinal and Transverse Profile Measure and Reporting procedure (EVEN Project) 1) . While there are various types of vehicle dynamics models or simulation Abstract: In case of fitting geometric model of pavement rutting to the real data, the model of a high order function has the well advantage of fitness. However, it also has the disadvantage of versatility. In this study, we developed the pavement rutting models with quadratic function and spline function for quantification of pavement rutting characteristics on road surface. The two developed models are verified in respect of the adaptability of these shapes and the accommodation for the simulation method of the vehicle dynamics using the road profile data of the PIARC EVEN experiment in 1998. As a result, it is indicated that the spline function is applicable for representing pavement rutting characteristics.