Study On Moisture Damage And Durability Of Asphalt Pavement With Long And Large Longitudinal Slope In Seasonal Freezing Zone

The mountainous and heavy hilly areas are widely distributed in the western part of China.With the rapid increase of the mileage of high-grade highways,the problem of ‘steep'and ‘long' slope is inevitable in the route design.The existence of long and steep slopes,on the one hand,makes driving speed slow down due to the deteriotated road pavement,especially in the effect of overloaded and heavy-duty vehicles.On the other hand,under the coupling of temperature,load and water,the asphalt concrete layer is prone to water damage,which normally caused looseness,falling particles,potholes,etc.on the asphalt pavement.Or if water enters into the interfacial layer of the asphalt pavement layers or between the surface layer and the base layer,the water will accumulate in the surface of the uncracked structural layers.Layers in between are easy to be slippery,resulting in discontinuity between the structural layers,which further aggravates the early damage of the pavement.Even in the same rainy area,the damage of non-long-slope roads is later than that of long-sloping road sections.Therefore,the early damage of the asphalt pavement on the long slope sections is required to be studied in depth,in order to improve the durability of the pavement to a certain extent,which is the problem that needs to be solved urgently.The early damage research of long longitudinal asphalt pavement mainly focuses on the formation mechanism and prevention measures of rutting,the composition design of asphalt mixture,and the interlayer damage of pavement structure caused by load force.Although many researchers have deeply studied the moisture damage of asphalt pavement,there are few studies on the mechanism of water damage and the damage of moisture Damage on asphalt pavement for the long slopes.In view of this,this paper mainly deals with the early damage problem of long and steep asphalt pavement,and systematically studies the performance deterioration law of long longitudinal asphalt pavement from high temperature stability,water stability and fatigue characteristics,in order to solve the problem of insufficient durability of the long longitudinal slope through the research of this aspects.The main research contents and conclusions are as follows:i.Under the coupling of environment,load and water during the service of long longitudinal asphalt pavement,the aging problem is more prominent.For the aging problem of rubber asphalt,it is explored by infrared spectroscopy,asphalt four-component test and GPC test for the content of asphalt components and changes in molecular structure during the aging process.ii.The fractal geometry theory is used to derive the formula for calculating the pass rate of intermittent graded aggregates.The fractal dimension of aggregates suitable for dense grade rubber asphalt mixture is determined,and the road performance of the rubber asphaltmixture using this grade is tested to determine the optimum mixing ratio for the grade rubber asphalt mixture.At the same time,in order to improve the drainage problem of long longitudinal asphalt pavement,the gradation of OGFC is determined based on the robust design principle.For the characteristics of the void structure of OGFC-13 asphalt mixture,the research is focused on the influence of the void ratio and semi-uniform void ratio to the duration of asphalt mixture.The attenuation momentum was used as an evaluation index for evaluating the moisture Damage resistance of OGFC materials,and the anti-blocking performance of OGFC mixture was tested.The results show that the attenuation momentum can effectively characterize the miosture damage resistance of OGFC mixture.iii.For the problem of moisture Damage to the long and steep asphalt pavement,the research is carried out from two aspects.The first one is to study the long longitudinal asphalt pavement.Firstly,using the momentum theorem,the mechanical calculation model of the dynamic pressure of asphalt pavement is established.The system analyzes the effects of vehicle load,driving speed and road longitudinal slope on hydrodynamic pressure.The second is to determine the void distribution characteristics of asphalt mixture by CT scanning technology,and construct a micromechanical model.Based on the cohesion theory,the influence on the moisture Damage of long and longitudinal asphalt pavement by the coupling factors such as the initial effective void ratio,void water saturation,freeze-thaw cycles,repeated load effects,etc.was studied.The assessment model of moisture damage under temperature-load coupling is established.It reveals the deterioration law of moisture damage to the asphalt pavement with long and large longitudinal slope based on mesostructure analysis.iv.Based on the viscoelastic theory,a three-dimensional finite element model is established.The effects of factors such as interlayer contact state,overload,longitudinal slope and vehicle speed on stability of long and large longitudinal slope asphalt pavement under the high temperature are analyzed systematically.The quantitative relationship of each factors with rut depth and maximum shear stress are determined.v.Based on the trabec bending test,the fracture energy between coarse aggregate and mortar,mortar and mortar in rubber asphalt concrete was determined.Based on this and the cohesive force constitutive model,as well as the criterion of interface fracture damage,the fatigue cracking characteristics for rubber asphalt concrete was studie.The crack cracking path was determined,and the meso-fracture fatigue equation of rubber asphalt concrete was established.