Simulation on the thermal contraction coordination behavior between asphalt mixture overlay and graded gravel base layer

Papers presented virtually at the 41st International Southern African Transport Conference on 10-13 July 2065The thermal contraction performance of asphaltic pavement structure is affected by the interaction between the bituminous layer and the granular layer underneath. The constraint action of the graded gravel base layer plays an important role in affecting the temperature strains in top asphalt layer. The focus of the present paper is to investigate the interactive thermal contraction mechanisms between the asphalt and granular base layers from a novel perspective. In this paper, a type of composite structure was proposed, and the dynamic and static strain acquisition system (DSSAS) was adopted to conduct the indoor thermal contraction tests. Combining the discrete properties of graded gravel materials (UAM) and the continuous characteristic of asphalt mixtures, the Finite Difference Method and Discrete Element Method (FDM-DEM) coupling models were established and calibrated. And the linear elastic and elastoplastic models of graded gravel layer were compared. Results show that the continuous-discrete coupling model has higher consistency with the laboratory test than the continuum model, and the relative error of thermal contraction coefficient is no more than 8.1%. The thermal strain-time curves of asphalt mixture and its composited specimens exhibit a nonlinear change law of first fast and then slow. And the asphalt mixture types and cooling temperature differences have little effect on the constraint action of unbound aggregate layer. The coordinated deformation between unbound aggregate base layer and asphalt mixture overlay can be realized by particle contact recombination, the inwardly extruded movement, loose on both ends and the middle compaction. Theoretical support for the research of low temperature crack resistance of graded macadam base asphalt pavement can be found in this paper