Study On Structure Of Asphalt Pavement Based On High Performance Of Graded Macadam Base

With the wide application of the semi-rigid base asphalt pavement structure in the expressway in our country,the defects of the reflective cracks and water damage are gradually revealed.The graded crushed stone is the base material of the flexible pavement,which has the advantages of strong seepage ability,no reflection cracks and relatively low cost.But at the same time,it also has the disadvantages of low strength,low shear resistance and easy to produce rut.With the addition of polypropylene fiber in the graded crushed stone,the shear shear strength is improved and the high performance graded crushed stone with good comprehensive performance can be formed,which can effectively avoid the shortcomings of the graded crushed stone.In view of this,it is of great practical significance to carry out the research on asphalt pavement structure of high-performance graded macadam base.In order to obtain high performance graded crushed stone,this paper refines the requirement of graded crushed stone aggregate in the current code,adopts the method of vibrating compaction to form graded crushed stone specimens,determines the optimum water content and maximum dry density,compares and studies the performance of high performance graded crushed stone and ordinary graded crushed stone.The results show that the high performance graded crushed stone is resistant to it.The shear strength(confining pressure 50kPa),splitting strength,CBR and unconfined compressive strength have been improved to varying degrees.The asphalt pavement structure of Graded Macadam Base is analyzed by HPDS2017.It is determined that the inorganic binder should stabilize the bottom tensile stress,the horizontal tensile strain of asphalt mixture bottom and the acceptance and deflection of road surface as the analysis index.Considering the different level of influence of different factors,the sensitivity analysis is made by L50(57)orthogonal test.At the same time,the influence degree of various factors on the research index is analyzed with extreme difference,and the change trend map of each factor level and each index is drawn,and the changes of the indexes when the modulus and thickness of different structural layers are changed are further discussed.The analysis shows that increasing the thickness of graded broken stone layer can effectively reduce the tensile stress at the bottom of the semi-rigid base layer,but at the same time,the tensile strain of the asphalt layer is increased,and the tensile strain of the asphalt bottom drawing and the semi-rigid base layer can be effectively reduced when the advanced modulus of gravel is proposed.The main factors of the bottom tensile strain of the bottom asphalt layer are the analysis.The main factors affecting the tensile stress of semi-rigid base course are the thickness of asphalt layer and the thickness of asphalt layer.The damage types of asphalt pavement structure of graded crushed stone base are analyzed,and the control indexes are determined by the tensile strain of the bottom layer of asphalt mixture,the permanent deformation of the asphalt mixture layer and the stable bottom tensile stress of the inorganic binder.Combined with different traffic load grades,the design index control model is used to determine the corresponding fatigue cracking equivalent axis of different traffic load grades,and the asphalt pavement structure of high performance graded crushed stone base is recommended for reference in practical application.The accelerated loading test of two asphalt pavement structures with graded crushed stone base and High Performance Graded Macadam Base was carried out by ALF acceleration loading equipment.The performance of rutting resistance was further studied.The results showed that the high performance graded crushed stone base had better anti rutting ability than ordinary graded crushed stone base.At the same time,the Abaqus finite element software is used to simulate the rutting of two kinds of pavement structures under high temperature acceleration loading,and the measured data and the finite element calculation data are compared and analyzed.The results show that the finite element numerical simulation can predict the asphalt pavement rutting effectively.At last,the high performance graded crushed stone base course was paved on the two Qin expressway,and its actual performance,construction technology and field quality control were studied to provide reference for other practical applications.