| Vehicle bump is the most universal disease in the expressway operation, which reduces the comfort degree and speed of the driving, the passing capacity of the roads, the service lives of the vehicles, and finally the using function of the roads. Relying on the Dianlin expressway scientific research project that is Study on Backfill Technology for the Back of Bridges and Culverts of Dianlin highway, this paper used the rigid-flexibility transition structure to prevent vehicle bump, which was effective. The results obtained in this paper provided technical supports for the similar treatment of the back of bridges and culverts in the southwest area and had a great significance to increase the expressway's social benefits, reduce their maintenance and repair cost, and improve the quality of expressways to be built.On the basis of a summary and analysis of research results of vehicle bump on the back of bridges and culverts at home and abroad, combining with the actual situation of Chinese highway construction, this paper analyzed and summarized the reasons and hazards of vehicle bump on expressways in china, analyzed the main characteristics of vehicle bump diseases and simplified the mechanical analysis of vehicle bump model on vehicle bump phenomenon. The main achievements and knowledges obtained as follows:(1)Causative mechanism and force of vehicle bump disease: the main objective factors of vehicle bump are as follows: the consolidation deformation of soil mass of earth subgrade, the additional compression deformation of backfill material, the cumulative plastic deformation of fill of retailing backwall under gravity loads and the difference of longitudinal slope between approach slab and embankment.Based on mechanical equilibrium relationship, the author calculated two kinds of vehicle bump-one was for the step formed without approach slab, the other was for the difference of longitudinal slope of the approach slab. The results showed that the appearing impact force had great connection with the step height and the weight of vehicles, namely, the faster, the heavier the vehicles were, and the larger the longitudinal slope was, the greater the appearing impact force.(2) Treatment measure research for preventing vehicle bump: considering the stiffness difference between abutment and foundation, between culvert retailing back wall fills and expressway embankment, with the analysis of domestic and overseas treatment methods and the characteristics of the back of bridges and culverts of Dianlin expressway, this paper used three kinds of treatment measures which were respectively"filler and approach slab","filler and transition step","filler and geotechnical grille"to implement the transition from rigid to flexibility ,and in actual design , using"filler - approach slab - geotechnical grille","filler- transition step-geotechnical grille- approach slab"to control the deformation from the design.( 3 ) Combining with Dianlin expressway's own characteristics, 5 of representative the backs of bridges and culverts were selected to be constructed with rigid-flexibility structure. The construction quality was controlled by the construction process requirement, the compactness detection, the field bearing plate test and the surface wave detection to achieve good effect for the rigid-flexibility transition structure.(4) To verify the effect of the rigid-flexibility transition structure in this paper, the settlement observation and the settlement regression analysis were made. According to the characteristics of backfill materials, three - dimensional numerical calculation and the rheological analysis for the backs of bridges and culverts were made and the stress- deformation features of the adopted measures were obtained. The detection results and the numerical results showed that the rigid-flexibility transition structure controlled the deformation of backfill materials and their stiffness was enhanced, so it played a great role in preventing the vehicle bump disease of highway. |
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