Pile Foundation Mechanical Characteristics Study Of Viaduct By The Road Of Operating Period Under The Bridge In The Deep Silt Soft Soil Area

Soil characteristic is high moisture content,large compressibility,low strength,slow consolidation in deep silt soft soil area.Upper thick back-fill soil and construction load cause soil produce some consolidation settlement during the construction process.Embankment load and vehicle load Continue to cause long-term consolidation settlement during the operation period.The pile will produce large negative friction resistance with the development of the consolidation settlement of soil.Pile will produce the drop-down by negative friction resistance.The negative friction resistance also cause additional settlement of pile foundation,which can lead to the upper structure form secondary stress.Small settlement affect the normal operation,the settlement of large lead to the damage of the structures.In this paper,using 124# pier of Yang huai he bridge as the engineering background in deep silt soft soil area,firstly use Zeevaert theory method to calculate drop-down load of pile group under embankment load,based on deep foundation method and the equivalent sum of slice to calculate the settlement of pile foundation of state.Secondly use PLAXIS 3D finite element software to establish single pile and pile group of natural foundation consolidation calculation model of under embankment loading,analysis of varying with concretion time rules of the single pile and pile group's pile foundation mechanical characteristics of pile top,the axial force of pile,pile side friction,neutral point position and surface settlement.Results show that numerical scattered data well agree with the simulation results.Thirdly the paper establish pile group foundation consolidation calculation model of composite foundation that road embankment height is 3.8 m of pile foundation of state,analysis of pile foundation mechanical characteristics and the influence of pile foundation existing for road subsidence in the road preloading period and operation period under the bridge.Finally,explore pile foundation mechanical characteristics changing with the consolidation time in different embankment height and lower underground water level.Conclusions can be predicted development development of negative friction ofpile foundation and pile foundation settlement,embankment settlement in the operating period for similar projects,at the same time can provide reference for design and construction of pile foundation in deep silt soft soil area.