Viscoelastic Nonlinear Multilayered Model for Asphalt Pavements

Flexible pavements are multilayer structures, typically with a viscoelastic asphalt layer followed by nonlinear unbound/bound layers. Conventionally, multilayered elastic analysis is performed to obtain the response of flexible pavements for design and inverse analyses; however, assuming asphalt pavement to be a linear elastic material is an oversimplification of its actual behavior. It is well known that the responses of asphalt pavements are both rate and temperature dependent. In the present work, a computationally efficient model has been developed to analyze flexible pavements, considering the top layer of linear viscoelastic asphalt concrete (AC), followed by a stress-dependent (nonlinear) base layer, and an elastic subgrade. Constitutive equations are formulated for layered viscoelastic-nonlinear axisymmetric systems. It is shown that the developed model can be used to simulate pavement response under stationary or transient loading. A comparison between the model responses and results obtained using a finite-element (FE) model shows that the model could be used to simulate both deflections and stress responses in multilayer viscoelastic nonlinear structures. The primary advantage of the model, as opposed to FE models, is its computational efficiency. This makes it viable for use in backcalculation algorithms.