| Rainfall can form a water film on the road surface,causing a sharp decrease in the friction between the tires and the road surface,posing greater risks for vehicles driving on slippery roads than in dry conditions,seriously affecting road safety.Porous asphalt pavement,due to its special large gap connection structure,can eliminate the water film on the road surface,inhibit water mist,improve anti sliding and other functions.However,in the case of a short extremely heavy rainstorm,its drainage capacity has reached the limit,and water film will inevitably appear on the local pavement,which will inevitably cause great safety risks to vehicles running at high speed.During the driving process of a car on rainy days,the splashes of water from the tires can easily form water mist under certain temperature,pressure,relative humidity,wind direction,and wind speed conditions.The visual characteristics of the driver are affected by visibility.Once water mist appears,the visibility ahead will significantly decrease,and the subjective recognition distance of the human body will also decrease rapidly,even leading to incorrect judgments of driving distance,resulting in traffic accidents.Compared to dense graded asphalt pavement,although porous asphalt pavement has significant functions in improving skid resistance and reducing water mist in rainy days,current research at home and abroad has only focused on the formation principle of water mist,without considering the impact of pavement structure on visibility.By adjusting the design parameters of pavement structure and rainfall to predict visibility,the safety performance of existing asphalt pavement will be significantly improved.This has important theoretical significance and application value for the linear design and operation guarantee of roads.This paper takes porous asphalt pavement as the research object,analyzes its pore structure characteristics,and establishes its correlation with the macroscopic drainage capacity of the pavement,such as permeability coefficient;Analyze the correlation between the thickness,porosity,slope,slope length,rainfall,permeability coefficient,and water film thickness of porous asphalt pavement.The study on the anti slip performance of porous asphalt pavement adopts indoor simulation of rainfall,analyzes the variation of friction coefficient of different asphalt pavement with vehicle speed and water film thickness,and analyzes the parking sight distance and driving stability of vehicles in rainy environments.Finally,taking the water mist generated by adjacent vehicles during driving as the research object,numerical simulation analysis and on-site demonstration were conducted on the changes in visibility caused by water mist generated by the water film.The main research conclusions are as follows:1)The average area of cross-sectional voids,average void fraction of cross-sectional voids,average area of individual voids,and effective diameter of individual voids in the void characteristics all increase with the increase of measured void fraction,showing a positive correlation;The average number of voids in the cross-section decreases with the increase of measured voids,showing a negative correlation;The average effective diameter of the gap is between 3-12 mm,which serves as the main drainage function of the road surface;2)Based on the influence of pore structure on the drainage capacity of porous asphalt pavement,an ultimate drainage strength index was proposed,and a regression model for ultimate drainage strength was characterized by drainage layer thickness,pavement cross slope,void fraction,and permeability coefficient;It was found that the thickness of the porous asphalt pavement surface water film increases with the length of the road drainage path,and rapidly increases with the increase of rainfall intensity;3)Based on the seepage characteristics of porous asphalt pavement,the concept of ultimate rainfall intensity and a calculation model for water film thickness of porous asphalt pavement under heavy rainfall were proposed,and the calculation model for ultimate drainage strength was modified;4)A regression model for the friction coefficient of porous asphalt pavement characterized by water film thickness and vehicle speed was proposed using the Streybeck curve;It was found that the larger the nominal maximum particle size,the better the anti slip safety performance of porous asphalt pavement;With the continuous increase of water film thickness,the stopping sight distance of porous asphalt pavement is smaller than that of dense graded asphalt pavement at the same speed;Under different weather conditions,the on-site braking distance of PAC-13 asphalt pavement is smaller than that of SMA-13 asphalt pavement,and the anti slip safety performance of porous asphalt pavement is significantly higher than that of dense asphalt pavement;5)A regression model for the visibility of asphalt pavement structure characterized by vehicle speed and pavement design parameters was proposed,and the mechanism of suppressing water mist and improving visibility on porous asphalt pavement was explored.It was found that the visibility caused by water mist continuously decreases with the increase of vehicle speed and water film thickness;The visibility of porous asphalt pavement can reach over 1.9 times higher than that of dense graded asphalt pavement under the same rainfall intensity.In this paper,a series of research work has been carried out on the void characteristics and drainage capacity of porous asphalt pavement,the prediction model of pavement water film thickness and skid resistance characteristics under heavy rainfall,and the suppression of water mist to improve safety performance,which has significant research significance for improving its traffic safety performance in rainy days.The research results provide a reference value for the practical application of porous asphalt pavement,especially for improving the level of traffic safety management and operation maintenance of existing roads,providing new ideas. |
PDF Full Text Request