Structure Analysis And Research Of Cement Concrete Pavement With Large Void Drainage Asphalt Overlay

Under the combined effect of traffic load and environmental factors,the expressway cement concrete pavement suffered serious damage to the original pavement,which greatly affected the pavement performance and service life.Cement concrete pavement can restore its pavement performance by adding drainage asphalt pavement layer,and improve the safety of driving in rainy days.This article relies on the project of "Key Technology Research and Demonstration Application of New Ecological Drainage Asphalt Pavement" of the Science and Technology Department of Guangxi Province,through indoor tests and finite element simulation,from the perspective of mechanical properties,quantitative analysis of the structure of cement pavement with drainage asphalt pavement under dynamic load The mechanical behavior provides a basis for engineering applications.First of all,based on the climate data and traffic survey data of Nanning city for nearly 30 years and the condition of the old cement pavement,the environmental and traffic characteristics of the Nanning round-the-city expressway in Guangxi were analyzed to provide traffic volume,structure,materials and other parameters for the mixture design and finite element simulation.The performance test of the raw materials,based on the coarse aggregate void filling method(CAVF)method,the target void ratio of 18%,23%,25% porous drainage asphalt mixture design,final determination of oilrock ratio: 5.3%,4.8% 4.7%,HVA content of high viscosity agent is 8% of asphalt content,polyester fiber content is 0.1% of the total mass of the mixture.Calculate the mass of the mixture with different porosity through the volume method,and use rotary compaction(SGC)to form PAC13(1),PAC13(2),PAC13(3)three grades of 150 mm × 170 mm specimens,and record the different grades The compaction curve shows that the coarse aggregate needs 220 rotations to achieve the indentation design void ratio PAC-13(1),254 times for PAC-13(2),and 180 times for PAC-13(3).For the PAC13(1)gradation,four test pieces with different compaction work are formed by controlling the rotation compaction times.Subsequently,core samples of 100×150 mm were drilled on the three grades and four compaction work specimens,and the void ratios after the test specimens and the core were compared,and the uniformity coefficient K of the void distribution of the drainage asphalt mixture was proposed,and the void distribution was evenly distributed.Sexual analysis.The results show that the porosity of the core of the SGC molded specimen is 2% to 4% lower than that of the molded porosity,and the porosity of the outer shell is 1% to 3% higher than the porosity of the molded specimen.Evenly.Then,through the asphalt mixture performance tester(AMPT),a semi-sine wave was used to conduct a dynamic modulus test on the three grades and four compaction work specimens of the mixed drainage asphalt.The influence law of temperature,frequency and gradation porosity on dynamic modulus is analyzed.The results show that the dynamic modulus of porous asphalt mixture increases with decreasing temperature,increasing loading frequency and decreasing porosity.According to the time-temperature equivalence principle(WLF),the main curve of the Sigmoidal model is fitted by the least square method to the dynamic modulus,and the main curve model of the dynamic modulus of three kinds of porosity PAC and the calculation of the dynamic modulus of different porosity are obtained Formula to provide material parameters for finite element simulation.Finally,the Abaqus finite element software was used to establish a threedimensional finite element model of porous drainage asphalt pavement with cement pavement under longitudinal and transversal cracks.The structural material parameters used indoor dynamic modulus test values.The dload subprogram written in Fortran language is used to simulate the moving load of the vehicle,and the parameters such as load size,period and speed are defined.The vertical stress of asphalt layer of pavement structure,the vertical displacement of pavement,the tensile stress and tensile strain at the bottom of the pavement,and the shear stress at the bottom of the pavement under different speeds and different structural combinations are studied.The results show that the load movement and the structural stress are not obvious.Monotonicity,the vertical compressive stress value of each layer of asphalt is 0～0.2Mpa.Calculate the permanent deformation of the asphalt pavement layer of the drainage pavement at 0.79～2.69 mm at different speed levels with three thickness combinations,which meets the requirements of the specification.Through inverse calculation,the structural optimization measures under different traffic conditions applicable to the project are proposed to provide a theoretical basis for the design of the cement pavement and the drainage pavement structure.