Study On Overlay Structure Of Old Portland Cement Concrete Pavement In Guangxi Municipality

The pavements constructed in early years are mainly Portland cement concrete pavements, in recent years, with the increase of traffic load and running speed, pumping area beneath the slabs increases which lead slabs crack or fault, many pavements are faced with reconstruction. Referring to the research result of overlay on old cement concrete pavements, this paper develops investigation on overlay on pumping cement concrete pavement.To begin with, developing investigation on using status of all types structure of overlay, put forward the project that reconstruct new cement concrete slabs on old pavements. Because of pumping area beneath slabs which seriously affect the life of pavements, Through the investigation of pumping area beneath cement concrete pavement slabs of QUANGUI expressway alternation project in GUANGXI municipality, the distributing regularity of pumping area is obtained. putting forward a new concept"pumping magnitude". Using three-dimension finite element method, analyzing stress of pavement slabs with pumping area, and also analyzing the effect of reinforced steel bar.Secondly, confirming the design indexes of overlay on old pavements, then using three-dimension finite element method to analysis the stress of the overlay. Combining with non-destruct test technique, such as FWD, parameters of old pavement are obtained, developing research on the design method of the overlay which base on pumping magnitude, establishing a set of pavement test appraisal and overlay design system.As inelastic property of gravel stone is mostly depended on it's grade, in order to predigest stress calculation , taking inelastic theory to analysis stress.This paper puts forward interlayer stress absorbing composite to resist reflection cracking which based on the study of reflective crack in overlay. Then particularly introducing it's application in Illinois state, and analysis it's mechanism which based on fracture mechanism-finite element method.In the end, the fatigue design method used in rehabilitation for old pavement has been validated through test road, then construction technique and control of interlayer stress absorbing composite and mortar grouting technique have been researched.