Relationship between Porosity and the Modified Constitutive Model Parameters of Asphalt Concrete Core Material

Porosity is a key control index for ensuring the compaction quality of rockfill dams with asphalt concrete cores. The porosity of the asphalt mixture is an important factor for an asphalt concrete core dam to obtain adequate strength and control the core deformation. However, the compaction quality (i.e., porosity) of the asphalt core wall inevitably exhibits spatial differences during actual construction process. To analyze the quantitative relationship between the porosity of the asphalt concrete core and the Duncan-Chang model parameters, triaxial tests under different confining pressures were carried out with asphalt concrete samples of different porosities. Based on the test results, the applicability of the Duncan-Chang model was assessed. Aiming at the limitation of the Duncan-Chang model, which is unable to characterize the strain softening and shear dilatancy of materials, a modified constitutive model of the asphalt concrete core was proposed. The determination method of the proposed model parameters was provided and verified by triaxial test results. A regression relationship was established between the porosity of the core material and the parameters of the modified constitutive model. This study provides a prerequisite for conducting refined finite element analysis on the mechanical performance of the asphalt core rockfill dams, taking into account the spatial differences in compaction quality of the asphalt concrete core.