| Theoretical Research and numerical simulation of overlaying composite asphalt pavement on old cement concrete pavement have been studied very widely, however, the study based on field monitoring and comparative study at the test evaluation on the specific structure is relatively lack. In view of this, the paper relies on physical test road project, focusing on studying dynamic evaluation method and engineering practice of overlaying composite asphalt pavement on old cement concrete pavement. The research contains numerical simulation of FWD dynamic analysis of composite pavement, FWD evaluation method of overlaying composite asphalt pavement on old cement concrete pavement, dynamic test detection of composite pavement test road on the site, structural performance evaluation of different composite pavement, Specific conclusions are as follows:Composite pavement structure under impulsive load deflection basin curve, the farther from load center distance, the smaller the value of the corresponding deflection of the measuring point, deflection value of each measuring point and the distance from load center into approximate inverse relationship. The fluctuating phenomenon is exist in the deflection time-history curve of each point,with time gradually decay to zero.Composite pavement deflection basin curve is approximately a convex curve, general deflection basin curve are obvious exist inflection point. Reflecting the asphalt overlay and old cement concrete slab modulus mutation, the asphalt structure modulus of the top surface is more soft relative to the slab, the greater the thickness, the greater the broken line.The most sensitivity factors that affect the deflection of Composite pavement is old concrete pavement’s modulus, followed by subgrade’s modulus and asphalt mixture’s modulus. Subgrade modulus of road does not change the deflection’s Line form of composite pavement, but it will change the whole deflection amplitude(all down parallelly), and the magnitude about the Deviation from zero of some Deflection point in the end. If concrete pavement overlaid by asphalt pavement features larger deflection and continuous deflection curvature, it means old concrete pavement crushed more completely.The variation characteristics that the deflection on the center of the top surface of the composite pavement influenced by the thickness increase of asphalt, is affect by the relationship between base modulus of road and the modulus of asphalt surface. When the modulus of old cement stabilized base smaller than the modulus of asphalt overlay, the deflection of composite pavement become smaller while the thickness of asphalt overlay become larger. When the modulus of old cement stabilized base bigger than the modulus of asphalt overlay, the deflection of composite pavement become larger while the thickness of asphalt overlay become smaller.The bearing capacity index and grading of composite pavement are presented, the representative deflection of the cement concrete pavement for the lower limit, the average deflection of asphalt pavement for the upper limit. The deflection dO of the road load center is put forward to evaluate the performance of the composite pavement, it express its performance is close to the trend of the asphalt pavement as soften coefficient index and grading.Evaluation eight kinds of typical composite pavement structure found that "white plus black" composite pavement structure can caryy more capacity than "white to black", the stress absorbing layer +12 cm AC composite pavement can bear the highest capacity. "white to black" composite pavement is more soft than "white plus black", old cement concrete pavement rubblization+20cmAC composite pavement structure diffusion coefficient was the highest, flexible best.Considering the composite pavement bearing capacity and diffusion coefficient. Suggest that the old cement concrete slab use the crack processing way in the old cement concrete pavement overlay asphalt composite pavement engineering. |
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