Shakedown of Subgrade Soil under Repeated Loading

Abstract

A new model for predicting the performance of a subgrade during soil compaction by rollers as a function of contact pressure and the strength characteristics of soils was developed. The model can be used to develop improved methods of pavement design, considering that the accumulation of plastic strains may continue under additional load repetitions or may cease to increase with time, indicating adaptation or shakedown conditions. To develop the mechanistic model of a subgrade, the homogeneous semi-infinite elastoplastic half-space under repeated loading was considered. By using a Mohr-Coulomb failure criterion, the boundary loads for which shakedown conditions or the steady state will be attained were determined. The residual horizontal normal stresses in the half-space were calculated and were shown to be in agreement with the measured distribution with depth. The theoretical and experimental results as they apply to soil compaction and pavement design problems are discussed. The required compaction contact pressure and the thickness of the compacted zone are estimated. The structural pavement design approach, considering residual normal stresses in a subgrade, is presented.