Fatigue Cracking Analysis Of Asphalt Pavement With Long Longitudinal Slope

With the development of China's transportation industry and the increase of the network density,the highway in the western region has welcomed a great development.Because of its geographical and geomorphic particularity,a large number of long and longitudinal slopes have appeared in the design of the western region.The long longitudinal slope has the following characteristics: one is the long slope,the total length and sometimes even more than four kilometers.Two,the slope is larger and the slope is more than 2%.Because of the characteristics of long and steep slope highways,diseases often fail to reach design and design years and economic effects.Through the field investigation and related research on the long longitudinal slope asphalt pavement,it is found that there are serious problems such as rut,fatigue and fatigue cracking.Because of the low speed of vehicles running on long longitudinal slope sections,the time between vehicle load and road surface is prolonged.It is well known that the viscoelastic properties of asphalt mixture are equivalent to high temperature according to the time temperature equivalence principle,which leads to the obvious decrease of the mechanical characteristics of the asphalt concrete.At the same time,because of the larger slope,the horizontal force of the road surface is much larger than that of the normal section.The greater the gradient,the greater the horizontal force of the road surface.On the other hand,the existence of cracks will cause the water to permeate along the gap,and the dynamic water pressure will be formed under the repeated action of vehicle load.Under the comprehensive influence of these factors,the early damage of the long longitudinal slope section is more serious.Therefore,it is of great significance to study the asphalt pavement of the long longitudinal slope.In this paper,the major longitudinal slope asphalt pavement section mainly has the following research(1)to analyze the structure characteristics of the long longitudinal slope section and the behavior of the vehicle load,the common disease and the cause analysis.(2)using the ABAQUS finite element software,the typical asphalt pavement structure is adopted,and the corresponding viscoelastic model is set up to analyze the dynamic response of the asphalt pavement under the action of double axis dynamic load.Then the stress state under different slope,speed and overload rate is analyzed.The variation characteristics of maximum shear stress under different factors are analyzed.(3)under the joint action of horizontal force and vertical force,the model of the crack in the long longitudinal slope is established by the ABAQUS finite element software,and the stress intensity factor is calculated,and the influence of the contact state,vehicle speed,different slope and the stress intensity factor in different layers is analyzed.(4)the fatigue life is calculated by using the Paris formula and the stress intensity factor calculated in the previous chapter,and the influence of various factorson fatigue life is found.On the basis of the above analysis,the laws of the factors affecting the disease are summarized,and the theoretical basis and reference are provided for the design and maintenance of the long and longitudinal slope asphalt pavement.