Study On The Mesoscopic Damage Behavior Of Drainage Asphalt Pavement Based On Void Distribution

The drainage asphalt pavement has good pavement performance such as drainage,noise reduction and skid resistance,and its performance comes from the connected void inside the mixture.Due to the alternate function of high temperature and rain in summer and cold freezing in winter in some seasonal freezing areas in China,the pavement damage caused by this is serious.The results show that under the action of freeze-thaw cycle,the strength and internal void structure of asphalt mixture will change,which will affect its durability,drainage and other pavement performance.On the other hand,as the drainage asphalt pavement belongs to the open gradation asphalt mixture,there is a large void in the pavement,which is easy to cause problems such as low strength and poor durability.Therefore,it is of great significance to study the characteristics of void distribution and its permeability in the drainage asphalt pavement,analyze the influence of freeze-thaw cycle on the strength and void structure of the drainage asphalt pavement,and reveal the mechanical response of the drainage asphalt mixture under the action of load.Based on this,this paper took the void as the main line,combined with X-ray CT scanning technology,image processing technology,three-dimensional reconstruction and finite element analysis method,to study the void evolution,microstructure damage and mechanical properties of the drainage asphalt mixture.In addition,the three-dimensional reconstruction model was used to analyze the permeability of the drainage asphalt mixture,and the information entropy theory of the image was introduced to determine the damage of the microstructure of the asphalt mixture.The main results of this study are as follows:First of all,three kinds of drainage asphalt mixture samples were designed and formed according to the requirements of the specification,and their voids and connected voids were measured.The results were compared with the values obtained from the reconstruction calculation to verify the reliability of the reconstruction.Through the permeability simulation of the reconstructed model,the permeability path and the permeability rate were visualized,and it was found that the horizontal drainage capacity of the drainage asphalt mixture was larger than the vertical drainage capacity.Secondly,analyzed the freeze-thaw cycles under the action of adding lignin fibers and the basalt fiber strength attenuation law of drainage asphalt mixture,on this basis,through the void,void volume distribution,void number analysis of the basalt fiber drainage asphalt mixture in 15 times freeze-thaw circulation space characteristics in the process of evolution,found that the early stage of the cleavage strength of asphalt mixture falling fast,leveling off late,and antifreeze performance of basalt fiber asphalt mixture is better;The void fractionincreases gradually,while the number of voids and the proportion of tiny voids decrease gradually.Then,by means of digital image logic operation,the damage of microstructure of asphalt mixture under the action of freezing-thawing cycle was explored,and it was found that there were three main forms of void evolution: some voids grew larger,and some adjacent voids connected with each other to form large voids or connected voids.Some of the voids get smaller and some of the voids disappear;New void can be formed after microcrack damage.The feasibility of using image information entropy to judge the structural damage of asphalt mixture is verified.Finally,the freeze-thaw cleavage test and uniaxial compression test were simulated based on CT scan data and numerical simulation technology.Through the freeze-thaw cleavage test,it was found that the asphalt mixture cracked under the action of load due to the large horizontal tensile stress.Through the uniaxial compression test,it is found that the bearing capacity of the mixture decreases with the increase of the void ratio.