A meshless hybrid boundary node method for solving top-down crack problems in pavements

摘要

Top-down crack is a type of cracking that rivals the severity and prevalence of reflective crack. It significantly reduces the pavement's quality service life. The initiation of these cracks has been explained by high-contact stresses induced under radial truck tires; however, due to the complex nature of the crack propagation in hot mixed asphalt (HMA) mixtures [1], the mechanisms for top-down cracking propagation have not been well explained.In this study, a combination of multi-domain hybrid boundary node method (Hybrid BNM) [2, 3] and fracture mechanics was employed to conduct physical representation and analysis of a pavement with a top-down crack. The Hybrid BNM, combining the moving least squares (MLS) [4] approximation and the modified variational principles, is a boundary-only, truly meshless method, which does not require a ‘boundary element mesh', either for the purpose of interpolation of the solution variables or for the integration of ‘energy'. In order to simulate the singularity of the stress on the tip of crack, enriched basis functions are used. In the enriched basis function method, the basis function must include important terms in the displacement field at the tip of a crack. To obtain the solution precisely, all terms in the displacement field at the tip of a crack should be included in the basis function. For convenience, the local enriched basis function √r is used to expand the basis function [5]. Comparing with the complete enriched basis function, the local enriched basis function has greater computing speed, and can accurately simulate the stress field at the tip of a crack well with fewer nodes.Finally, the multi-domain Hybrid BNM is implemented in a comprehensive parametric study to explore the mechanisms of crack propagation in a given pavement structure. The factors, which influence the stress intensity factor (SIF) and the expansion path, e.g. horizontal load, thickness of asphalt concrete (AC) layer and base, AC layer and base modulus, are investigated through numerical results. It can be concluded that the Hybrid BNM, which has high convergence rates and high accuracy, is adapt to solve top-down crack problems.