Elastic modulus of subgrade is an important input parameter in the multilayered elastic structural analysis of asphalt pavement, and the resilient modulus measurement of subgrade materials which assumed action of the vehicle load has been examined energetically after 1990's by laboratory testing. However, no design example using the resilient modulus is shown in the Japanese pavement design book because of the resilient modulus is a non-linear elastic modulus depending on a stress state, and structural analysis becomes complicated. In this study, by using the rearranged past data, arranging method of the resilient modulus was examined and furthermore a simple calculation method of the subgrade resilient modulus for the multilayered elasticity structural analysis was proposed.

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 The deterioration processes of pavement are compound ones characterized by surface deterioration as well as capacity. This study proposes a methodology to nd the optimal inspection policy for road pavement with uncertain deterioration processes. Since the deterioration progresses are characterized by a lot of uncertainty, the pavement conditions cannot be deterministically evaluated unless the inspection or repair activities are carried out. The road administrators have to make the decisions of whether repair should be implemented based upon the results of inspection. In this paper, the value of the inspection is evaluated by use of real option theory, and the optimal inspection and repair model is formulated to investigate the optimal inspection frequencies an repair policy which may minimize the expected life cycle costs. Finally, the validity of the methodology presented in the paper is investigated by a case study dealing with the expressway in the real world.

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