Study On Key Influencing Factors Of Permeability Coefficient Of Road Asphalt Mixture

With the rapid development of highway construction and the continuous improvement of traffic service level,the phenomenon of early disease is gradually highlightened,resulting in the use of asphalt pavement performance and life expectancy is lower than the design level.Many researches show that the existence of water is the main factor of early damage of asphalt pavement.Water damage is one of the most important types of early damage.Asphalt concrete pavement water damage is the result of water effect together with the vehicle load,water movement in the asphalt concrete pavement is a question of permeability,it is due to rainfall into the asphalt pavement inside that caused water damage problems.Asphalt pavement permeability is affected by many factors.Therefore,the law of pavement permeability changes with the key influencing factors is beneficial to further deepen the understanding of water damage of asphalt pavement and reduce the damage of early water.The purpose of this paper is to reveal the changing rule of the asphalt concrete pavement permeability.First,this paper investigates the situation of highway in Chongqing.Then analyze the influencing factors of permeability and determine the degree by using gray correlation analysis,get the degree from large to small order is:porosity>maximum particle size>2.36mm pass rate>0.075mm pass rate>asphalt dosage>asphalt needle degree.Then according to the needs of the test,the method of Darcy's law as the guiding principle of self-made osmosis instrument,using the unstripped specimen to solve the problem of leakage in the test side wall,and developed pressure osmosis instrument.And do experiments through the independently developed test instrument.In order to obtain the results of different gradation type and different state of segregation.Analysis the relationship between segregation and void ratio with permeability.The permeability coefficient increases with the degree of segregation,and the water seepage capacity of the mixture with larger particle size is obviously increased under mild gradation,the mixture with smaller particle size still has good anti-permeation ability.After the separation,the anti-permeability performance of the mixture does not meet the specification requirements.The permeability coeficient of the mixture decreases with the increase of the compaction temperature,and the mixing temperature has little effect on the permeability.If other conditions meet the specification,when the compaction temperature exceeds 130?,the mixture is basically impermeable.Asphalt mixture after the porosity of more than 7%permeability coefficient significantly increased,and the degree is getting bigger and bigger,the penetration rate and penetration total have obvious change when the permeability coefficient surpass 85ml/s(0.OOlcm/s).Finally through pressure test simulated dynamic water pressure to analyze the changing rule of permeability under different flowing pressure.The hydrodynamic pressure is proportional to the square of the driving speed,and the permeability coefficient increases with the increase of the hydrodynamic pressure.After the hydrodynamic pressure reaches 0.3Mpa,the mixed material specimen with the porosity is 5%-7%began to obviously seepage.