Study On Structural Analysis For Large Stone Asphalt Mixes Of Asphalt Pavement

According to its composition material's mechanical properties, the base can be divided into the flexible base, The semi-rigid base and the rigid base. The semi-rigid base has its merits such as high overall intensity, better board character, strong supporting capacity, advantageous material selection and so on. but its own shrinkage fracture causes reflection crack in asphalt pavement. The rigid base asphalt pavement has its merits such as better integrity, high supporting capacity, strong anti-washout, mild-mannered road surface, easy service and so on. but its rigidity is high, its easy reduction and air shrinkage causes fracture, reflection crack also exists in the rigid base asphalt pavement. Therefore, it is necessary to develop research on anti-reflection crack measures for crack alleviation layer, and explore new asphalt pavement structure.This dissertation has mainly covered the study work on three aspects as follows: (1) According to the basic theories of pavement crack mechanics and Finite Element Modeling (FEM), reflection crack propagation path is numerically simulated for Large Stone asphalt Mixes(OLSM) of asphalt pavement. (2) 3-D FEM is used to analyze vehicles load stress, temperature stress and coupled stress for OLSM of asphalt pavement. (3) Through the comparative coupled stress analysis for OLSM of asphalt pavement and Asphalt Concrete(AC) of asphalt pavement, Discussion on anti-crack mechanism is held for OLSM.The research indicats that as follows: Under combined action of vehicles load and temperature, reflection crack does not propagate in straight line upward to asphalt pavement, but propagate in"zigzag"line; Especially in OLSM layer, reflection crack propagation path is cut off by the pore and getting more zigzag when it encounters pore; The zigzag degree of reflection crack propagation path is decided by these factors such as thickness and porosity of OLSM, shape and distribution form of pore and so on; More zigzag reflection crack propagation path is, longer the time that crack propagats from bottom to top in asphalt pavement are, as a result the service life of asphalt pavement are prolonged. For vehicles load stress, its major effect factors include axle load, thickness of OLSM and thickness of asphalt concrete layer; For temperature stress, its major effect factors include temperature decrease scope, module, thickness and porosity of OLSM, module and thickness of asphalt concrete layer; For coupled stress, its major effect factors include temperature decrease scope, thickness of OLSM, thickness of asphalt concrete layer. OLSM consists of more great size aggregate, few asphalt content and less porosity, the propagation path around crack tip can be effectively blocked by this porous structure, the transmission ability of the tensile stress and tensile strain is weakened, thus pavement structure stress is dissipated and absorbed. In addition, the contraction coefficient of OLSM is small, its great particle size and porous structure has strong plastic deformation ability, it absorbs strain energy that released by crack fully, and reduces stress concentration phenomenon around crack, thus postpones the upward propagation speed of reflection crack. The anti-crack effect of OLSM is significantly better than general AC alleviation layer.