A generalized Drucker-Prager viscoplastic yield surface model for asphalt concrete
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2014, RILEM. A generalized DruckerPrager (GDP) viscoplastic yield surface model was developed and validated for asphalt concrete. The GDP model was formulated based on fabric tensor modified stresses to consider the material inherent anisotropy. A smooth and convex octahedral yield surface function was developed in the GDP model to characterize the full range of the internal friction angles from 0 to 90. In contrast, the existing Extended DruckerPrager (EDP) was demonstrated to be applicable only for a material that has an internal friction angle less than 22. Laboratory tests were performed to evaluate the anisotropic effect and to validate the GDP model. Results indicated that (1) the yield stresses of an isotropic yield surface model are greater in compression and less in extension than that of an anisotropic model, which can result in an under-prediction of the viscoplastic deformation; and (2) the yield stresses predicted by the GDP model matched well with the experimental results of the octahedral shear strength tests at different normal and confining stresses. By contrast, the EDP model over-predicted the octahedral yield stresses, which can lead to an under-prediction of the permanent deformation. In summary, the rutting depth of an asphalt pavement would be underestimated without considering anisotropy and convexity of the yield surface for asphalt concrete. The proposed GDP model was demonstrated to be capable of overcoming these limitations of the existing yield surface models for the asphalt concrete.
