Research On The Typical Structure And Material Parameters Of Freeway Pavement In Northeast

Widespread diseases exsit in asphalt pavement in Northeast expressway. Besides the increasing overloading day by day, whether the pavement structural design and material properties are good or not are also the main reasons leading to the diseases in asphalt pavement. Therefore, how to design reasonable pavement structure according to natural conditions, material source and traffic conditions in northeast and put forward appropriate material parameters are of great significance.In order to realize the purposes,this paper carries out the following studies.1,According to the climate conditions in Northeast, based on the standard "Technology Guide for Frost-proof Design and Construction of Highway Engineering" of Ministry of Communication, road frost areas in Northeast are divided into especially heavy frozen area, heavy frost area and intermediate frozen area. According to traffic survey data, the PADS software is used to predict the cummulative traffic load of 29 major trunk roads in the coming 15 years in Northeast. And the traffic classification in Northeast is simplified as intermediate, heavry and expecially heavy grades.Taking into account regional differences and economic factors, modulus of resilience while meet the requierements of material and structure in northeast highway is determined. At the same time, soil strength grade is divided using PADS software.2,The paper carries out systematic studies on the material parameters of asphalt surface layer, semi-rigid base and flexible base. The main results are as follows.(1)Given the non-adaptabtive of asphalt selection criteria and climate characteristic in northeast, PG graded method for asphalt selection is proposed. Also, the grade standard is recommended. In gradation aspect, stage filling method is presented to optimize the aggregate gradation. Based on the test results in laboratory, high and low temperature performance parameters are brought forward for asphalt mixture used in highway surface in condition of different traffic and climate. The following results all provide references for asphalt selection and the control of asphalt mixture performance parameters during the construction of typical structure.(2) In combination with design and construction experiments for semi-rigid base in northeast and previous study results, base on the design principle of interlocked, volume method is used in the mixing proportion design for lime fly-ash road base material.And the gradation range is recommended. through the related test validation, reasonable strength indicators for lime fly-ash stabilized macadam material, frost resistance indicators and resistance to shrinkage performance indicators are proposed, which provide a basis for the seclection and design of typical structure base material.(3) In combination with test results in laboratory and using status of flexible base, structure type, molding method and modulus and so on are recommended for flexible base material in norhteast highway, which can be used for reference for selection of the structure form of flexible base material and construction index control.3,Considering the development level of economic in Northeast China, semi-rigid base is also the main type when the typical structure is put forward in Northeast China. Also, the Composite base asphalt pavement is proposed in order to make up for the lack of a single base type though the combination of flexible base and semi-rigid base to improve the pavement performance and durability.The typical structure is checked using Shell program and pavement analysis & calculation software and finite element program。Final typical structure is proposed.Meanwhile, considering the thickness of frost cushion is smaller and the consideration is lack in frost design, according to the thickness calculation for frost cushion in "Technology Guide for Frost-proof Design and Construction of Highway Engineering" of Ministry of Communication, the thickness scope of frost cushion for three kinds of typical pavement structure in condition of different frost area, differentsoil dry and differentwet type and frost depth is proposed.In short, the study results have great significance in improving pavement structure qualtiy, reducing pavement early disease, extending service life, saving cost and maintenance cost.