| In recent years,frequent urban waterlogging has become an important problem to be solved in urban construction.The results show that using permeable base material to strengthen the rainwater infiltration capacity of pavement structure is an effective way to alleviate urban waterlogging.As one of the permeable base materials,large stone permeable mixture(LSPM)not only has high strength,but also can prevent semi-rigid base asphalt pavement reflection cracks and other diseases,so it has broad application prospects in the future urban road construction.As the key design parameter of permeable material,the change of void ratio will directly affect the performance of LSPM.However,the current mix design method can not directly obtain the mix ratio corresponding to the target void ratio;based on the above problems,this paper optimized the mix proportion of LSPM on the basis of the existing open graded asphalt mixture design method,and studied the performance of the optimized large stone permeable mixture(OLSPM).On this basis,combined with the specific engineering situation,the permeable asphalt pavement structure with olspm was designed,and finally the application effect of the pavement structure was evaluated by using SWMM software.Firstly,in view of the deficiency of the existing mix proportion design method,this paper used the classification standard of coarse and fine aggregate in Bailey method,introduced the step-by-step filling test,i-method gradation design method,effective asphalt dosage formula and absorbed asphalt dosage formula,powder binder ratio,etc.to supplement and optimize CAVF method,and a design method for the mixing ratio of large-diameter permeable asphalt mixture based on the target void ratio was initially proposed.On this basis,the asphalt content was verified by leakage test,the molding method was determined by comparing the volume parameter changes and specimen appearance of Marshall compaction test and rotary compaction test in the molding process,and the mix proportion characteristics of OLSPM-25 were analyzed by comparing the gradation and asphalt content of LSPM-25 under the same porosity in the specification.The final experimental and analysis results show that the amount of asphalt calculated by this method can meet the requirement of leakage loss;Rotary compaction method is suitable for OLSPM indoor cylindrical specimen forming method,and the porosity should be taken as the compaction index to control olspm in this process;At the same void ratio,OLSPM-25 has more finer fine aggregates and therefore leads to a relatively larger amount of asphalt.In addition,the 4.75-19 mm coarse aggregate content in its coarse aggregate is also higher than that of LSPM-25.Secondly,in order to further improve the verification of the above mix proportion method,LSPM-25 and LSPM-30 were introduced as the control group to evaluate the road performance,water permeability and mechanical index of OLSPM.The results show that: due to relatively high asphalt content and good skeleton structure,the freeze-thaw splitting strength ratio of OLSPM-25 and 30 is higher than that of LSPM-25 and 30,and OLSPM has good water stability;the fatigue life times of OLSPM-25 and 30 are higher than that of LSPM-25 and 30,and OLSPM has good fatigue performance;Although the permeability coefficient of OLSPM-25 and 30 is slightly lower than LSPM-25 and 30,both of them are >0.2cm/s and the difference is not significant in numerical value.OLSPM-25 and 30 have good permeability function;The dynamic modulus of OLSPM-25 and 30 is higher than LSPM-25 and 30,and OLSPM has good mechanical properties.Thirdly,based on the traffic volume of Zheng Deng expressway overhaul project in Zhengzhou,this paper selectd the structure form of permeable asphalt pavement with OLSPM base,calculated the corresponding design indexes of these structure form under different thickness of structure layer by using Abaqus,and optimized the results by using orthogonal analysis.Finally,the semi permeable permeable pavement structure with drainage asphalt mixture PAC as the surface layer,OLSPM as the upper base,cement treated porous base CTPB as the lower base,waterproof and crack suppression coiled material with sand cushion as the cushion was determined.The results show that the surface course is the main factor affecting the permanent deformation and shear stress of asphalt pavement,and the base course under CTPB is the main factor affecting the bottom tensile stress of inorganic binder layer.Except the cushion,the increase of the thickness of each structural layer lead to the decrease of permanent deformation of asphalt pavement,the decrease of bottom tensile stress of inorganic binder layer and the increase of surface shear stress.Finally,the semi permeable permeable pavement structure with OLSPM base is determined,which is 11 cm in surface layer thickness,12 cm in OLSPM layer thickness,36 cm in CTPB layer thickness and 5cm in cushion layer thickness.Finally,after determining the structure form and thickness of the permeable pavement,this paper selectd the two-way six lane road within a certain length of the project as the study area,and took the surface runoff coefficient,peak flow and peak time as the characterization indicators of surface runoff,and used the urban stormwater management model SWMM to quantify the surface runoff of the study area before and after the application of the permeable pavement structure.The results show that the surface runoff coefficient decreases by 71.28%,69.27% and 68.67% respectively,and the peak flow decreases by 78.55%,75.66% and 74.74%respectively under the rainfall return periods of 10,50 and 100 years,the reduction effect of the above indexes decreases with the increase of the return period;the peak time is delayed by 5min,3 min and 3 min respectively,and the increase of return period had no significant effect on the delayed effect.OLSPM semi permeable road has good control effect on urban road surface runoff. |
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