Research On Mechanical Response And Environmental Benefit Of Trunk Highway Asphalt Pavement Constructure In Chongqing

In order to optimize the pavement structure from two aspects of the mechanical performance and environmental benefit of asphalt pavement structure,which can improve the service life of Chongqing trunk highway and introduce the concept of sustainability.This paper takes the asphalt pavement structure of Chongqing trunk highway as the research object.First,conducting the detailed statistical analysis of Chongqing trunk highway about the operating environment characteristics,traffic characteristics and structure style of the asphalt pavement;Secondly,testing the dynamic modulus of AC13 and AC20 asphalt mixture by the simple performance test(SPT),determining the dynamic modulus master curve function under 25? by 1st Opt software to provide material parameters for the analysis of the dynamic response of asphalt pavement structure;Then,simulating the dynamic response of pavement structure by finite element analysis software,studying the influence of temperature and speed and axle load on the mechanical response,analysissing the relationship between pavement structure parameters and the dynamic response index in order to optimizing pavement structure design by adjusting the parameter of pavement structure with orthogonal analysis method;Finally,quantitatively analyzing the environmental benefit during the construction of typical asphalt pavement structures of Chongqing trunk highway based on the LCA concept,and studying the influence of pavement structure parameters on the energy consumption and carbon emission during the whole construction period.The main research results of the paper are as follows:(1)Chongqing trunk highway running environment is divided into four regions based on the GIS method combined with the annual rainfall,annual mean maximum temperature in the hottest month,annual extreme minimum temperature,the regional differences in traffic characteristics and pavement performance are quite obvious.The main asphalt pavement structure of Chongqing trunk highway is mainly 4cm +5cm/6cm +20~25cm +20~25cm,the single structural form is inconsistent with the complex climate and traffic situation in Chongqing.(2)Under the action of dynamic load,the vertical compressive strain of the top surface of the subgrade is less than the static load,while the tensile stress at the bottom of base course,the vertical pressure stress and the shear stress of asphalt layer are all larger than the static load;with the increase of axle load,the dynamic response indices all increase under the load time and space distribution;Compared with the high speed condition,the tensile stress at the bottom of base course,the vertical compressive strain,the pressure stress and the shear strain of asphalt layer are relatively higher under low speed condition,and the shear stress is relatively lower,and all the mechanical indexes at low speed are more sensitive to the velocity change;In addition to the shear stress,all mechanical indexes increased with the increase of temperature,the mechanical response index under the isothermal model was higher than the temperature gradient model,which overestimate the fatigue life of semi-rigid base course and the permanent deformation of asphalt layer.(3)The tensile stress at the bottom of base gradually decreases with the increase of the surface thickness,the thickness of the base course and the modulus of the base,and the order of influence is the thickness of the base layer> the surface thickness> the base modulus;The compressive strain at the top of the roadbed decreases with the increase of the surface thickness,the base thickness and the base modulus,and the order of influence is the thickness of the base layer>the surface thickness,>and the base modulus;The vertical compressive stress of asphalt layer decreases with the increase of surface thickness,increases with the increase of base thickness and base modulus,and the order of influence is surface thickness>base modulus >base thickness;The shear stress of asphalt layer increases with the increase of surface thickness,decreases with the increase of base thickness and base modulus,and the order of influence is surface thickness>base modulus>and base thickness.(4)The energy consumption and carbon emission of the construction period of asphalt pavement in Chongqing under considering energy raw material is more than that without considering the energy of raw materials;The production of cement is always the main source of energy consumption and carbon emissions under the unit project,followed by the mixing stage of asphalt mixture,and the aggregate transportation segment significantly affected by distance;the energy consumption and carbon emissions of mechanical construction under the condition of shorter distance is far greater than the material transport stage,however,the energy consumption and carbon emissions of mechanical construction under the condition of longer distance is not more different than the material transport stage and even lower than the material transport stage;Under the condition of considering raw material energy,the transportation distance of aggregate is reduced by 1km,the energy consumption under functional units is reduced by 7027 MJ and carbon emission is reduced by 326.74kg;Under the condition of considering raw material energy and shorter transportation distance,the energy consumption of the functional unit is reduced by 7.9% and the carbon emission is reduced by 5.6% when the energy type of the mixing plant is changed from heavy oil to natural gas.(5)When optimizing the parameter of pavement structure,under the condition of considering raw material energy and shorter transportation distance,when the content of cement in the base is increased by 1%,the total energy consumption in the construction period increases by 113206 MJ,and the total carbon emission increases by 16435.8kg;when the thickness of the surface layer is increased by 1cm,the total energy consumption in the construction period increases by 113042.7MJ,and the total carbon emission increases by 2981.8kg;when the thickness of the base is increased by 1cm,the total energy consumption of the functional unit increases by 41465 MJ and the total carbon emission increases by 4839 kg.