Study On Pore Clogging Behavior And Recovery Technology Of Drainage Performance Of Double-layer Drainage Asphalt Pavement

Compared with the traditional single-layer drainage asphalt pavement,the double-layer drainage asphalt pavement has more prominent advantages in drainage,anti-skid,noise reduction,and frost resistance.The void volume will still be reduced,and the functions of drainage,anti-skid,and noise reduction will decline,due to factors such as vehicle load and clogging substances deposition,even if the problem of pore clogging is prevented at the design level of double-layer drainage asphalt pavement.For the problem of pore clogging of drained asphalt pavement,the main maintenance measures at present are high-pressure washing,vacuum cleaning,manual cleaning and the combined use of multiple technologies.Such cleaning and maintenance measures need a lot of manpower and material resources,which is easy to lead to the failure of the adhesion of aggregates on the surface of drainage asphalt pavement and the looseness of the surface.It has been found that the negative hydrodynamic pressure can provide a large vacuum suction force.So,it is necessary to explore the internal seepage characteristics of double-layer drainage asphalt pavement and the self-cleaning technology of clogging under the action of hydrodynamic pressure.Thus,the clogging behavior,the formation mechanism of hydrodynamic pressure and its distribution in double-drained asphalt pavement is firstly studied in this thesis,and then the clogging substances self-cleaning mechanism and its effect in double-drained asphalt pavement.The drainage performance recovery technology of double-layer drainage asphalt pavement is proposed,which is of great significance to the maintenance,extension of service period,and large-scale application of double-layer drainage asphalt pavement.Firstly,the double-layer drainage asphalt pavement model with different void volume and layer thickness combination s was established based on the discrete element method(DEM),and the clogging substances with different particle size distribution is added for natural deposition,which reveal ed the deposition state of the clogging substances in the pavement.Then,the seepage model of double-layer drainage asphalt pavement was established by computational fluid dynamics(CFD)-DEM method,and the law of the influence of seepage flow on the depth of the clogging substances was studied.The results show that the accumulation of small particle size clogging substances centered on large particle size and the common accumulation of clogging m substances in multi particle size range were the main reasons for the pore clogging of double-layer drainage asphalt pavement;The influence of void volume and clogging substances gradation on the distribution of clogging substances in pavement was significant;Seepage flow had a great influence on the clogging depth of the clogging substances with particle size less than 0.3 mm,while the influence on the clogging substances with particle size greater than 0.3 mm can be ignored.Secondly,a hydrodynamic pressure model considering the hydrodynamic behavior of complex pore structure was established based on DEM and CFD methods.The formation mechanism of hydrodynamic pressure was revealed through numerical simulation,and the hydrodynamic pr essure distribution laws at different depths of double-layer drainage asphalt pavement under the influence of different factors were studied.The results show that the pressure gradient formed inside the road surface after the tire squeeze d the water film was the main cause of the hydrodynamic pressure cycle;The hydrodynamic pressure distribution show ed an alternating trend of positive and negative,and the value of negative hydrodynamic pressure was generally slightly less than that of positive hydrodynam ic pressure;With the increase of vehicle speed,water film thickness and vehicle load,the hydrodynamic pressure values at different pavement thicknesses show ed different degrees of increasing trends;When the thickness of water film was less than the depth of the tread depression,the hydrodynamic pressure value increase greatly,while when the thickness of the water film was greater than the tread depression depth,the change trend of the hydrodynamic pressure value bec ame slower;The h ydrodynamic pressure of the lower layer of the double-layer drainage asphalt pavement was significantly lower than that of the upper layer.Thirdly,in order to explore the mechanism of self-cleaning caused by hydrodynamic pressure and self-cleaning effect of clogging substances in double-layer drainage asphalt pavement,the hydrodynamic pressure value was extracted,and the user-defined function(UDF function)of positive and negative hydrodynamic pressure cycle was established.The UDF function was added at the boundary condition to simulate the self-cleaning effect of hydrodynamic pressure cycle caused by tire movement on the clogging substances in the pavement.It is found that the water in the pores of the pavement flowing from the bottom of the lower layer to the pavement surface will wash out the clogging substances inside the pavement under action of negative hydrodynamic pressure,and some of the clogging substances can be sucked to the pavement surface;Partial clogging substances inside double-drained asphalt pavement could be cleaning by hydrodynamic pressure,and the self-cleaning mass of the clogging substances increased with the increase of vehicle speed,water film thickness and wheel load;The self-cleaning ability of the hydrodynamic pressure to the clogging substances gradually decreased with the increase of the pavement depth;The self-cleaning effect of clogging substances with a wide particle size distribution was the best under the same hydrodynamic pressure.Finally,in order to explore the effect of clogging substances on the drainage performance of double-layer drainage asphalt pavement and the restoration effect of maintenance measures on drainage performance,the bottom of the rutting plate specimen of the double-layer drainage asphalt pavement was sealed.The drainage performance and recovery effect of double-layer drainage asphalt pavement under multi-factors were studied through multiple clogging and flushing tests on rutted plate specimens.The research results show that regular c leaning of double-layer drainage asphalt pavement with high-pressure water gun can effectively restore its drainage performance;The maintenance effect was best when the pavement was slightly clogging;Clogging substances with a wide particle size distribution had a greater impact on the permeability coefficient of double-layer drainage asphalt pavement and its recovery effect;the overall recovery effect of drainage performance after high-pressure water gun flushing was g ood,and it was recommended to use high-pressure water gun for continuous flushing twice.