Modification of Japanese Pavement Fatigue Life Criteria by Considering Climatic Effects in Cold Regions

Abstract

In Japanese pavement design method, fatigue life criteria for cracking and rutting come from the US Asphalt Institute model, which relates failure loading number to the tensile strain on the lower surface of the asphalt mixture layer and the compressive strain on the top layer of the subgrade, respectively. These strains closely relate to the moduli of each layer. Japanese pavement design method assumes the moduli of base and subgrade layers are constant throughout the whole year. However, as proven by numerous past studies, these moduli are strongly affected by variation of water content and freeze-thaw cycle. To be precise, rising water content, as a result of the inflow of water or the thawing of ice lenses, causes a temporary decrease in the stiffness of subgrade and base course material. Besides, ice formation tends to break some of the particle contacts and interlocking of soil particles, which also leads to a degradation of base course material. Basically, climatic effects (variation of water content and freeze-thaw cycle) on base and subgrade layers material are not fully captured in Japanese pavement design method now. This study calculates the fatigue life of eight local flexible pavement projects with variation of base layer moduli considering freeze-thaw action and seasonal fluctuation in water content to capture the effects of climate on the fatigue life of the pavement. Long-term measured performance data are used to calibrate the rutting model. Results proved that climate-related degradation of the granular base decreases the fatigue life against rutting of asphalt pavements in cold regions.