LABORATORY VERIFICATION OF A MECHANISTIC SUBGRADE RUTTING MODEL (ABRIDGEMENT)

This study attempts to simiplify the analysis and appication to engineering design of a previously developed model. The experimental data indicate that the rutting parameters (A and m) are generally functions of the dynamic modulus and the applied dynamic stress. The dynamic modulus characterizes the material properties; i.e., it accounts for the water content, the dry density, and the soil structure as far as rutting criteria are concerned. The parameter m is almost constant for normal and dense soils, but may decrease slightly for very wet soils. There is a relation between the parameter A and the dynamic modulus E. The data show a linear relation betwen log A/E and log 1/E that is dependent on the applied dynamic stress level. Analysis of the results obatined by Montoya at different environmental conditions, verifies the uniqueness of the log A/E versus log 1/E relation. That is, the environmental changes are reflected in the dynamic modulus E and consequently in the values of parameter A by which permanent deformation can be evauated. A generalized model is presented in which the deformation for a subgrade soil layer is calculated. The subgrade layer is divided into imaginary sublayers, the permanent strain is computer for each, and the total contribution of the subgrade in the total pavement deformation is obtained from an equation.