STRESS DISTRIBUTION IN SUBGRADE SOILS AND APPLICATIONS IN THE DESIGN OF FLEXIBLE PAVEMENTS

A comprehensive study of stress distribution in highway subgrades of flexible pavements was conducted. A stress-dependent non-linear finite element method (FEM) program, ARKPAVE, was used to generate structural responses of pavements under vehicle loads. The subgrade depth of interest was found to be around 1500 mm. The confining pressure is recommended to be the chamber pressure in triaxial and/or repeated load testing in the evaluation of subgrade soils. The distribution of deviator stress along the subgrade depth was found to be more or less independent of the layer thickness combinations. It is shown that the stress at the top of the subgrade is a better criterion than the vertical resilient strain. This stress was mapped out in accordance with the various thickness selections including full-depth asphalt concrete (AC) pavements which can be readily incorporated into a modern pavement management system. The contours of deviator stress at the top of the subgrade also facilitate the optimum design of flexible pavements as demonstrated in the paper by a design example. This approach advocates the feasibility and promptness of the adoption of rational mechanistic-empirical (M-E) design methods for pavement structures. (A)