Study On Mechanical Charactics Of Asphalt Pavement With Cracks

Currently, the construction of highway in our country is in a rapid development phase, but early damage to the highway in service is a common phenomenon, especially the cracks of asphalt pavement based on semi-rigid type base. The cracks of asphalt pavement will certainly change stress state of itself, accelerate the speed of destroiration, shorten its working life. This also shows the mechanical analynsis model of traditional asphalt pavement structural design is far from being perfect, and dosen't reflect the actual status of the structure in most of all its life. The purpose of this dissertation is based on the study on the mechanical characteristics of asphalt pavement with cracks, acting by temperature load and vehicle load, so as to master the rule of cracking generation and propagation, to direct the design, construction, maintenance of asphalt pavement.Firstly, the temperrature field of asphalt pavement was presented through numerical simulation by finite element mothod. Based on climatological and thermal theory, this dissertation got numerical solution of one-dimensional unsteady temperature field under natural boundary condition, the solution accorded with the distribution law of road structure. This established basis for analysis and study on temperature stress in the next chapters.Secondly, the statical charatiristics of asphalt pavement with a crack was presented. Based on the state of asphalt pavement crack , the finite elment analynsis model was set up, included mechanical model with a cross-crack and mechanical model with a expanding crack. To the former, the result indicated that ,acted by vehicle load, the structure of asphalt pavement with a cross-crack is being worse stress state; To the later, based on fracture mecanics theories, the stress intensity factors was adopted as the parameter reflecting the stress condition at the crack tip. The result shows key factors effecting the expanding of crack are modulus of asphalt surface layer and the thermal coefficient of contraction of base layer, the effect of tempreture load is more than that of vehicle load.Thirdly, the dynamical charatiristic of asphalt pavement with a crack was presented. Based on dynamic theory, the finite elment analynsis model, including mechanical model with a cross-crack and mechanical model with a expanding crack was set up. To the formerl, this dissertation has been done modal analysis and harmonic reponse analysis. The result indicates that, since the crack emerged in asphalt pavement, its dynamical charatiristic has been changed greatly, such as inherence frequency and vibration model. To the later, this dissertation has been done transient dynamic analysis, calculated the stress intensity factors changing with the damp of asphalt pavement, the cycle of load action and the parameters of pavement structure.This dissertation is supported by the engineering of Beijing to Qinhuangdao freeway. The research has done a full-scale research on the mechanical charatiristic of aspalt pavement with cracks, the research result can provide theory base for design method to prevent the crack extend and research on long term charatiristic of asphalt pavement .