| Pavement crack is one of the most serious pavement diseases of Expressway in Shanxi Province.In the case of limited maintenance funds in Shanxi Province,highway maintenance departments need to allocate a lot of funds for crack treatment every year,but the maintenance effect is still not ideal.In this paper,the causes and forms of Shanxi highway pavement cracks are deeply analyzed,and a crack classification method with strong pertinence and operability is formed to help the maintenance department preliminarily classify the pavement cracks and take targeted maintenance measures,so as to improve the crack treatment effect and save maintenance funds.First of all,this paper conducts a large-scale investigation on the pavement crack of important expressways in Shanxi Province to fully grasp its morphology and distribution characteristics.The investigation results show that the cracks are mainly tranverse joints through the pavement and the longitudinal joints within the range of wheel tracks.The spacing of transverse joints is 20 ～ 30 m,the average density of longitudinal joints is 0.87m/m,and the interlaced network cracks of longitudinal and transverse joints appear in most sections.Secondly,core samples were drilled at typical fractures,and 3D fractures were reconstructed by using CT scanning technology and mimics software to study the fracture mode and 3D morphology.The analysis shows that there are four cracking modes of pavement cracks in Shanxi Province,which are top-down,bottom-up,top-down development and top-down penetration.Among them,the low-temperature transverse crack is a top-down cracking,with large development depth and wide water seepage channel,which has a great impact on the pavement;the longitudinal crack in wheel load area and block net crack are also a top-down cracking mode,but the downward propagation path is tortuous and the water permeability is low.The bottom-up cracks are usually semi-rigid base reflection cracks.In special cases,the base cracks will produce corresponding cracks in the asphalt surface,forming top-down development cracks and top-down penetration cracks,which will cause great damage to the pavement.Thirdly,this paper establishes the meso model of random aggregate with interface transition zone by MATLAB software,simulates the generation of surface cracks and the expansion process of reflection cracks of asphalt mixture pavement through ABAQUS finite element software,and explores the influence of different factors on crack expansion.The results show that the surface cracks will genetate at many points at the same time on the road surface,so there will be a zigzag and discontinuous phenomenon in the process of fusion development.The reflection crack tip stress concentration phenomenon is obvious,and it will propagate under the load far lower than the tensile strength of the material,and the propagation path is single.Aggregate distribution,initial crack length,tensile strength of interfacial transition zone and load distribution have no obvious influence on the main cracking modes,but they will affect the crack initiation point,cracking load and propagation path to a certain extent.Finally,this paper combs the main causes of the pavement cracks of Shanxi expressway,and puts forward the classification method of pavement cracks based on the cause analysis.The test results show that this method has strong operability and high classification accuracy.Through large-scale sampling and crack seepage test,this study explores the development law of different crack depth and its impact on the pavement,and finally puts forward targeted maintenance measures according to the characteristics of cracks. |
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