Study On Reasonable Structure Of SMA Asphalt Pavement In Western Inner Mongolia

Asphalt horseshoe grease(SMA)structure has better road performance than traditional asphalt concrete pavement(AC)structure,so it has been widely used in road construction in recent years,but with the sharp increase of traffic volume and overload in recent years,SMA pavement also began to appear different degrees of damage.Among them,the lack of pavement structure design method is the main factor leading to the disease of SMA asphalt pavement.Compared with the numerical simulation method,the traditional asphalt pavement design method is too complicated,and the pavement structure design index is too simple,which cannot fully and effectively analyze the pavement structure failure form and achieve effective and obvious control effect.Therefore,this paper conducts in-depth investigation and analysis on the damage mechanism and reasons of SMA pavement in western Inner Mongolia,and adopts the finite element software simulation method.The mechanical evaluation index was used to accurately evaluate the stress of the internal structure of the pavement,timely control the climate and environmental factors and load traffic and other factors,and put forward the SMA pavement structure form suitable for the western region of Inner Mongolia,and the following conclusions were obtained:(1)The mechanical response of the pavement model under the continuous action of static load is higher than that under dynamic load.(2)A comparative analysis of the thickness,modulus and load of the three factors affecting pavement structural indexes found that with the gradual increase of the thickness of the surface layer and the base layer,the improvement benefits of various mechanical indexes became lower and lower.Compared with the change of the surface layer,the increase benefits of the base layer thickness were slightly larger.Therefore,blindly increasing the thickness of the structural layer would undoubtedly increase the cost.The overall structure of the road surface is recommended to control the upper layer between 4～6cm,the middle layer between 5～7cm,the lower layer between 6～8cm,and the base thickness should not be greater than 3 0cm.In terms of modulus factors,the influence of base modulus on mechanical response is obviously greater than that of the modulus of the surface layer.With the increase of the modulus of the surface layer,the mechanical response shows a decreasing trend,and the base modulus has a significant impact on the fatigue life of the surface layer.Too large base modulus will lead to the increase of tensile stress of the asphalt surface and the base layer,but the base modulus is too small.It will cause the pavement structure to fail to reach sufficient strength.Comprehensive analysis shows that the base modulus should be between 8000 and 12000Mpa,and the base modulus should be controlled between 7000 and 1 0000Mpa.The influence of load factors on the mechanical response of pavement structure is much greater than that of modulus and thickness.When the load level increases from 0.7MPa to 1.4MPa,the mechanical response indexes of the overall pavement structure show a significant increase trend,and the tensile stress of the bottom layer of the pole-free mixture layer increases by 3 4%.The tensile strain of asphalt mixture layer increased by 32.3%.The vertical compressive strain of the top surface of the subgrade increases by 20.5%,so the increase of traffic volume and the occurrence of overloading will greatly increase the probability of road diseases,which is not conducive to extending the service life of asphalt pavement structure.It is recommended to control the thickness of the surface layer between 15～20cm,the thickness of the base layer between 40～50cm,the modulus of the base layer between 80,000～10000Mpa,and the modulus of the bottom layer between 7000～80000Mpa for medium and heavy load traffic roads.For heavy traffic roads,it is recommended that the thickness of the surface layer be controlled between 18 and 22cm,the thickness of the base layer be controlled between 50 and 60cm,the modulus of the base layer be controlled between 10,000 and 12000Mpa,and the modulus of the bottom layer be between 8,000 and 1 0000Mpa.(3)The temperature field of typical asphalt SMA pavement structure in western Inner Mongolia was constructed using ABAQUS finite element software,and the mechanical response of pavement structure under the sequential coupling method of temperature and load was obtained.The results were imported into the dynamic load model,and the analysis showed that the tensile strain of asphalt mixture layer under the combined action of load and the most unfavorable temperature reached 95 με in summer.In winter,it reaches 80με,which is consistent with the results of similar studies.It is found that the influence of ambient temperature on pavement structure under dynamic load is much greater than that caused by load change.This study provides some suggestions for structural optimization and road life extension of SMA asphalt pavement in western Inner Mongolia.