Study On Permeable Asphalt Pavement And Subgrade Mechanical Response

In China,the construction of the sponge city is being vigorously advocated.The application of the permeable pavement is an important component of the construction of the sponge city.It has many advantages,which can ease the pressure on water resources,reduce the city water logging stress,noise and alleviate the greenhouse effect.However,because of the large void ratio,the reduction of the contact area between the aggregate and the aggregate will result in the reduction of the material strength.This is especially true in the area of traffic load superposition.In order to explore the mechanical response characteristics of the permeable layer and other structural layers under different types of loads,In this paper,porous asphalt pavement and its roadbed are selected as the research object,and the performance parameters of asphalt mixture are obtained through experiments.Discrete element analysis software is used as the tool to establish the two-dimensional discrete element model of each structure layer,and its mechanical response rule under traffic load is analyzed.First,five layers of pavement structure are selected,4cm OGFC-13 upper layer,5cm AC-16 middle surface layer,7cm AC-20 under layer,20 cm cement stabilized macadam base,20 cm graded gravel cushion.The subgrade is the soil,and the parameters were selected by the related simulations and the standards.The gradation composition of three kinds of asphalt mixture was designed.The optimum oil and stone ratio of OGFC-13 was determined by the calculation of asphalt film thickness,whose result is 4.6%,Leakage test and Cantabro test were used to test.The Marshall test was used to determine the optimum oil stone ratio of AC-16 to 4.8%,and the best asphalt content of AC-20 is 4%.Water stability of three kinds of asphalt mixtures was tested by immersion Marshall Test and Freeze-thaw Splitting Test.The high temperature stability of three kinds of asphalt mixtures was tested by rutting test and Triaxial test.The results show that the road performance of the three kinds of asphalt mixture meets the requirements of the standard.Then,a numerical model of each structure layer based on two dimensional discrete element method was established.And through the adjustment of the simulated boundary conditions,the contact among with particles is ideal.According to the stress-strain curve of asphalt mixture based on the triaxial test,the parameters of the model were calibrated to ensure that the numerical model consist with the actual.Finally,the structure of each layer was calculated and analyzed under three types of load,which are static load,vertical vibration load and uniform moving load.Through the above test and calculation analysis,It is found that the surface layer of permeable asphalt is most affected by the load.So it is necessary to have enough carrying capacity.The stress time at the bottom of the surface layer is different from that of the cushion and the base of the soil base.Due to the structure effect of rigid plate body,the ultimate tensile stress usually occurs at the bottom of the base layer,when the tensile stress is allowed to exceed the allowable stress,the initial crack will be produced,which leads to the destruction of the pavement structure.Shear stress is the main cause of pavement cracks.The combination of the bituminous layer and the base is the most vulnerable part of the shear failure.