A fracture-based constitutive model for pavement interface characterization

This paper presents a new fracture-based constitutive model to characterize pavement interfaces. The constitutive model captures the entire range of interface responses from fully bonded (initial elastic) to fully debonded. Failure (debonding) mechanisms can occur in the following states which the model also captures: pure shear, pure tensile, shear with compression, and shear with tension. Additionally, the developed model shows promise for characterizing cracking problems. In this model, an interface constitutive relationship has been implemented with a frictional Mohr-Coulomb plasticity model. The constitutive model and interface elements were implemented by means of the user element (UEL) of ABAQUS finite element (FE) software. An algorithmically consistent tangent operator for the interface elasto-plastic modulus was used to facilitate convergence. Non-associative plasticity was implemented to have a better control of volumetric expansion (dilation) at the interface element. Debonding was formulated by a nonlinear softening model integrated into an elasto-plastic constitutive model. The model addresses frictional properties, including pressure dependency of the interface shear strength and dilation due to roughness of interfaces. This paper provides numerical examples and discusses the experiments conducted for characterization of hot-mix asphalt (HMA) overlay and Portland cement concrete (PCC) interfaces, including tests on direct shear at various temperatures, tack coat materials, tack coat application rates, and concrete surface texture. As part of the experiments, three-dimensional interface elements were inserted on a predefined failure plane. Load displacement responses obtained from direct shear tests were in agreement with the finite element simulations. The developed model with its inherent frictional nature is ideal for use with interface problems especially under various loading conditions (pure tensile, pure shear, shear with compression, and shear with tension). The model can also be further advanced to be used in the finite element analysis of pavement cracking problems under mixed-mode loading.