Study On Skid Resistance Of Asphalt Pavement Surface Layer

Since the reform and opening up,China’s expressways have developed rapidly,but traffic accidents often occur.Among the many factors affecting traffic accidents,the lack of skid resistance is the most important one.Relevant field investigation found that improving the skid resistance of road surface can effectively avoid the occurrence of traffic accidents.In view of this,this paper carries out research on the anti-skid performance of surface layer,mainly from the types and properties of anti-skid surface materials,composition design of asphalt mixture,anti-skid performance of asphalt mixture,anti-skid decay law of asphalt pavement surface layer and other aspects.Firstly,the characteristics of highway sections are analyzed(such as curved slope section,longitudinal slope section and curved slope combination section).Based on the analysis of road alignment,vehicle driving force characteristics and other aspects of highway sections,starting from the mechanics theory of skid resistance demand,it is concluded that the standard for road to meet the requirements of skid resistance is friction coefficient not less than 0.137.Secondly,select different aggregates,determine the mineral composition of the aggregate,wear value,abrasive value and other physical and mechanical indicators,found that the hardness of the aggregate mineral content is smaller,the aggregate corresponding to the abrasive value is also larger,the corresponding wear value is smaller,its skid resistance durability is better.Thirdly,three commonly used asphalt mixtures ac-13,SMA-13 and PAC-13 were selected as research objects,and the corresponding indoor specimens were formed.The sliding resistance of different asphalt mixtures was evaluated by pendulum method,spring dynamometer method,sand paving method and clay method.It is found that PAC-13 mixture has the largest friction coefficient,swing value,structure depth and average texture depth,among which AC-13-2 mixture has the best sliding resistance,indicating that appropriate coarse gradation can improve the sliding resistance.Through digital image analysis different anti-sliding performance of asphalt mixture,obtain surface texture and extract the angle of each interval number,point density and area density,we evaluate the texture indexes such as combined with the coefficient of friction,found that each mixture interval angle number of similar,PAC-13 than AC-13 mixture of various mixture density is small,area density is big,compared with SMA-13,it has higher point density and smaller area density,and the measured friction coefficient is large,and the friction coefficient in the initial state of each mixture is much higher than 0.137,which meets the requirements of anti-skid road.Finally,based on the rut test to simulate the wear process of the actual road surface,the friction coefficient of asphalt mixture was measured by the wear test of asphalt mixture in stages based on the factors such as mixture type,temperature and freezing-thawing.At the same time,the image information was obtained,and the texture indexes such as angle number,point density and area density were extracted.It is found that with the increase of abrasion times,the attenuation range of friction coefficient is relatively fast in the early stage of various mixtures,and gradually tends to be flat in the later stage.With the increase of temperature and the effect of freeze-thaw,the attenuation range of friction coefficient becomes faster.The surface texture of the mixture is sparse in the early stage,and the single area is small,and the measured friction coefficient is large.In the later stage,the surface texture becomes clustered,and the measured friction coefficient is small because the single area is large.The friction coefficient of each mixture at each wear stage is obviously greater than 0.137,which meets the anti-skid requirement of road surface.When controlling a single variable,the greater the rut depth,the greater the absolute value of friction coefficient attenuation.The analysis results of relevant image indexes extracted by digital image processing technology show that: No matter in what test environment,the change of the contact surface between wheels and asphalt mixture is due to the movement of aggregate,wear and filling of mortar.The point density and angle number of each interval of skeleton PAC-13 and SMA-13 mixture will decrease with the increase of wear times,and the area density will increase continuously.The angle number,point density and area density of the suspended AC-13 mixture will increase with the increase of the wear coefficient.