Discrete Element Analysis Of Asphalt Mixture Failure Mechanism And Verification Of Particle Contact Model

In recent years,my country has made significant progress in the field of transportation construction.In terms of road construction,asphalt pavement has always been valued as a high-grade pavement,but many of the damage phenomena that occur during the service of many asphalt pavements cannot be ignored.There are many types of damage to asphalt pavement,and the phenomena of tensile failure and bending failure are particularly significant.Therefore,studying the influencing factors and destruction mechanisms of these two types of destruction phenomena is an important work that has received much attention.The split test and three-point bending test in the laboratory test are simple to operate,and the internal stress state of the test piece is close to the actual working state of the asphalt pavement,so it is more suitable for studying the tensile failure and bending and tensile failure of asphalt mixture.The main contents of this article are:(1)The crushed stone and asphalt used in the pavement construction produced by the Xiangtan Huawang Asphalt Mixing Plant are used to obtain the basic mechanical properties of asphalt and stone materials through basic physical experiments of asphalt,stone materials and mineral powder.Using the AC-20 grading with the best oil-rock ratio determined by the research group to make Marshall compaction samples,a split test at three temperatures was carried out with a UTM testing machine and a Marshall stability tester.(2)Carried out the asphalt mixture particle contact model test,designed the sample preparation and auxiliary loading device for the asphalt mixture contact model test,and carried out three temperature conditions of 0 ℃,15 ℃ and 30 ℃ for the cement stone rod sample The tensile,compression and shear mechanical tests are used to determine the relevant mechanical parameters of asphalt mortar.The test results show that as the temperature decreases,the tensile strength,compressive strength,and shear strength of the cemented stone rod increase.The compression curve becomes a law of strain softening after the peak compressive strength;the decrease in temperature will inhibit the viscous effect of the cement,making the speed of stretching and shearing force decrease after the peak point accelerated,and tends to be more brittle.Comparing the three mechanical responses with the discrete element contact model,the results show that the mechanical responses are basically consistent.(3)The microstructure model of the asphalt mixture split test was established to verify the feasibility of the contact model test designed in this paper and the rationality of the contact parameters.The influence of loading rate,gradation and void ratio on the peak value of axial force in the split test is analyzed.The results show that for every doubling of the loading rate,the peak value of axial force increases by about 25%;in the same gradation range,The peak value of axial force will increase with the increase of the proportion of coarse aggregate,under different gradation conditions,the peak value of axial force will decrease with the decrease of the maximum nominal particle size;for every 1% increase in porosity,the peak value of axial force Reduced by about 5.7%.In addition,the tensile failure mechanism in the split test is revealed,and it is discussed that strengthening the strength of the asphalt pavement surface and bottom asphalt mixture can effectively suppress the asphalt pavement tensile failure.(4)A three-point bending test model of asphalt mixture was established to analyze the effect of loading rate,gradation and voidage on the flexural and tensile properties of asphalt mixture trabecular specimens under the same strain conditions.The results show that under the same strain rate conditions When the loading rate is doubled,the number of cracks increases by about 87%;with the increase of the maximum nominal particle size,the number of cracks in the test piece increases by about 62%;the porosity of the asphalt mixture increases by 1% The increase in the number of cracks is 20%.Among the three types of influencing factors,the loading rate has the greatest influence on the bending and tensile properties of the specimen,followed by gradation,and the lowest void ratio.In addition,the bending and tensile failure mechanism of the three-point bending test is revealed,and the two methods of strengthening the strength of the bottom asphalt mixture at the loading position of the asphalt pavement and improving the uniformity of the aggregate distribution in the asphalt mixture can effectively suppress the bending and tensile failure of the asphalt pavement.