Research On Asphalt Pavement Mechanical Responses And Performances Of National And Provincial Trunk Roads

Adverse traffic load factors and environmental factors result in the condition that pavement distresses of trunk roads tend to be complicated and serious.However,studies on pavement mechanical responses in China are mainly associated with the static modulus of asphalt mixtures,which ignores constitutive properties of asphalt mixtures.Besides,there are a few studies involving vehicle driving characteristics and environmental factors.This paper,using the typical structure of Chongqing trunk roads as a case,analyzed the influence of traffic factors and environmental factors on pavement responses and performances of national and provincial trunk roads.Firstly,based on the investigation and analysis of traffic factors,environmental factors and distress characteristics in Chongqing,it was found that the road performance of Chongqing trunk roads was affected by special terrain as well as regional and seasonal effects from temperature and humidity.The growth of traffic volume was fast,the overloading problem was serious,as well as main pavement distresses were cracks and minor pavement diseases were rut and water damage.Secondly,the dynamic modulus prediction equation of asphalt mixture was selected.Physical and mechanical properties of AC-13(SBS modified asphalt)and AC-20(70#matrix asphalt)were determined by indoor tests,which provides material parameters for asphalt mixture dynamic modulus prediction model.Then,in order to ensure the accuracy of model calculation,the appropriate load action form and model boundary condition were selected,and the model size and grid size were analyzed.In addition,mechanical analysis indicators and pavement performance indicators were determined.Furthermore,using the finite element software ABAQUS and the pavement performance prediction model,the most unfavorable mechanical response positions were determined,effects of axle loads,driving speed,slope(horizontal load),temperature and subgrade humidity(groundwater level)on mechanical responses of the typical structure were analyzed and pavement performance sensitivity analysis related to above-mentioned factors was undertaken.The results showed that,all mechanical indicators were significantly influenced by axle loads,and the small proportion of overloaded trucks seriously reduced fatigue life of base course and accelerated the permanent deformation of asphalt layer;the fatigue life of base course at 20 km/h speed section was only 57.3%of that at 80km/h speed section;different vehicle driving characteristics on longitudinal routes caused the sharp increase of maximum shear stress at the pavement surface,which can cause the shear failure and shear flow deformation;Temperature had a great effect on each mechanical indicator,and the cumulative fatigue damage of base layer and cumulative permanent deformation of asphalt layer in the multi-temperature range were larger than those in the single-temperature range;the fatigue life of sections with a larger h value(the distance between groundwater level and subgrade top)was greater than that of sections with a lower h value;the influence level of traffic and environmental factors on the fatigue life of base layer was as follows:proportion of overloaded trucks>driving speed>temperature correction factor>groundwater level;the influence level of traffic and environmental factors on the permanent deformation of asphalt layer was as follows:pavement equivalent temperature>proportion of overloaded trucks,and driving speed and groundwater level had no significant effect on the permanent deformation of asphalt layer.Finally,according to distress characteristics and mechanical analysis results,the prevention and control measures were proposed for Chongqing’s national and provincial trunk roads,which provides references for trunk road structural design and distress prevention.