Analysis On Structure Characteristic Of Rubblization And Asphalt Overlay Pavement Based On Falling Weight Deflectometer Data Backcalculation

Rubblization is one of old cement concrete pavement rehabilitation techniques. This method not only breaks former old PCC, the broken layer serving as base course layer or subbase layer in overlay pavement has high bearing capacity, but also has good effect to prevent reflection cracks. Rubblization has developed for more than twenty years in foreign countries, in the domestic we still locate introducing and testing phase in this field.Base on foreign engineering experience, the modulus of rubblized PCC is the deciding factor in AASHTO guide for AC overlay design, this modulus must be tested on field. Falling weight deflectometer (FWD) as high efficiency surface deflection testing equipment, simulate vehicle dynamic load perfectly and measure the deflection basin exactly. Using deflection basin backcalculation modulus is more convenient than bearing plate test, and through about thirty years'research, the result of modulus almost fit the engineering standard.In view of this, Using FWD equipment test rubblization engineering and backcalulate modulus of every stage of rubblization, through the modulus result evaluate the quality of engineering and supply reference data to AC overlay design. The mainly conclusion contains:Toward different pavement material, using linear modulus, spherical stress correlation modulus and deviator stress correlation modulus build numerical simulate model. Add optimization arithmetic in this model act as the backcalculation program. Nonlinear backcalculation research indicate that when detect at pavement surface, the stress in subgrade usually small, the nonlinear behavior of soil is insignificant; Backcalculation of rubblized PCC show that this layer has nonliear property, the average modulus underneath the load plate area is greatness than other area and the total average modulus of rubblized PCC is close to gradation aggregate, it has enough bearing capacity serving as base course layer or subbase layer; The result of backcalculation using static load need to modify, it is advised that cement concrete is 1.5, cement treated aggregate base is 2.0, rubblized PCC is 1.25-1.4, subgrade is 3.0; It is suggested that if the deflection sensors's coefficient of variation is less than 3.0, than use the average value to backcalculate, alse use each point data to backcalculate.