Study On Differential Settlement Forecasting Between New And Old Pile Foundation In Bridge Widening

The problem of controlling settlement difference between new and old bridgefoundation is one of technology difficulties, many bridge widening engineering aredue to improperly treatment of settlement difference, more sever diseases appear andhuge economic losses are caused not long time after highway opening to traffic. Atpresent, there are more researches on bridge pile foundation settlement, but theattention of researchers and engineering designers is pile foundation total settlement,while few researches on bridge pile foundation settlement difference. In term of beambridge widening engineering, old bridge foundation settlement have been almostfinished, new bridge foundation settlement still increases with time, so deeplyresearching on the growing trend of old and new foundation settlement and makingpredict on their settlement difference have an important engneering meaning onproperly selection of upper structure joint style and time and reducing the disease afternew and old bridge having been jointed.On the basis of study results at home and aboard, this paper systematicallyanalyzed the beem bridge’s widen way and desease causes. Combined with the widenproject of Zheng-Luo expressway, field monitoring was conducted on the pilefoundation settlement of three bridges, the results showed that the new bridge pilefoundation has different levels of settlement deformation under the combined actionof structure load and construction load at different consruction stages, the settlementdeformation increased with time, while the growing rate obviously decreased. Basedon the grey system method, the grey system prediction model of widening bridge pilefoundation settlement was built, and the foundation settlement difference of the threebridges was seperately predicted, through comparison with field measurement, thepredicted value agreed well with the measured value, which proved that the greysystem method can scientificly predict the foundation settlement difference betweenthe old and new bridge.This paper achievement has an important engineering practical value for beambridge widen projects, with a strong pertinency and applicability. Meanwhile, it has acertain guiding significance for perfecting the bridge design and constructionspecification.