Numerical Simulation of the Reflective Crack Propagation Path for Open-graded Large Stone Asphalt Mixes

The reflective cracking in asphalt surface is a technical problem that exists in the semi-rigid base asphalt pavement structure and the rigid base asphalt pavement structure, how to control its emergence and development is still a major problem for road engineering. At present, researches on the anti-cracking performance for Open-graded Large Stone asphalt Mix (OLSM) in China almost remain in the test road observations, very few study the mechanism of its anti-cracking from the mechanical point. Aiming at this problem, according to the basic theories of pavement fracture mechanics and Finite Element Modeling (FEM), the reflective crack propagation path is numerically simulated for OLSM of asphalt pavement. The research indicates that as follows: Under combined action of vehicles load and temperature, the reflective crack does not propagate in straight line upward to asphalt pavement, but propagates in "zigzag" line; Especially in OLSM alleviation layer, the reflective crack propagation path is cut off by voids and getting more zigzag when it encounters voids; The zigzag degree of the reflective crack propagation path is decided by these factors such as thickness and percentage of voids of OLSM, shape and distribution form of voids and so on; More zigzag the reflective crack propagation path is, longer the time that crack propagates from the bottom to the top in asphalt pavement are, therefore the service life of asphalt pavement are prolonged. OLSM consists of more great size aggregates, low asphalt content and few percentage of voids, the propagation path around the crack tip can be effectively blocked by this porous structure, the transmission ability of the tensile stress and tensile strain is weakened, thus stress in the pavement structure is dissipated and absorbed.