This paper describes the initial development of a two-dimensional finite-element chip seal model subject to loads from truck tyres. A linear viscoelastic constitutive model represented by a Prony series is used to simulate behaviour of the bitumen. Aggregate particles are treated as rigid and incompressible. The chip seal layer is represented by a digitised image of the cross-section of an actual seal. Modelling of tyre loads takes into account the inflation pressure of the tyre, the stiffness of the tread rubber and the texture profile of the chip seal. Contact between the tyre and the chip seal generally occurs only on aggregate asperities. Validation of the bitumen material model has been by means of dynamic shear rheometer measurements and tensile tests. In this preliminary study,three penetration grades of bitumen (40/50, 80/100, 180/200) are studied at three truck travel speeds (30 km/h, 50 km/h and 80 km/h). Results indicate that (1) maximum stresses are largely independent of binder grade or loading rate, and (2) strains increase as binder penetration grade increases but decrease with increasing loading rate. This confirms practical observations that chip loss is most likely to occur with soft binders subject to slow loading rates. (a).
Samenvatting