a deformation model for flexible road pavements

rigorous methods for the computation of stress and permanent deformation distributions generated in a pavement by a moving wheel, which satisfy the equations of equilibrium and compatibility simultaneously with the constitutive equations for the materials concerned, are difficult and time-consuming to apply in practical cases when the materials exhibit creep (permanent deformation). a simpler approximate method of deriving the permanent deformation is described, based on separating the computation of stress and transient elastic strain from the computation of deformation; it is assumed that, as in practice the permanent deformation occurring during a single pass of a wheel is extremely small compared with the transient elastic strain, the stress distribution is essentially unaffected by it. because of this separation, the deformation distribution will in general not satisfy the compatibility conditions, and in addition "free slip" conditions are implicitly assumed for all interfaces in the pavement. some results obtained using a computer program embodying the analysis are presented; in the absence as yet of adequate materials-characterisation data the computations were performed using hypothetical deformation laws for the materials. the results are qualitatively plausible, and throw some light on the relation between the behaviour of a pavement under a moving wheel and under a stationary pulse load. (a)