Settlement model of bridge pile group foundation in soft soil stratum

Based on the settlement characteristics of bridge pile foundation on soft soil stratum,the similarity rule of pile group model in this geological situation was derived.The indoor model of pile group foundation with pile cap was self-designed and analyzed.The test results show that the additional stress attenuates with the increase of depth and its distribution form approximates as triangular form within the scope of the pile body.At the same time,the vertical stress of pile-side soil increases as the settlement of pile top increases correspondingly.Moreover,the vertical stress of pile-side soil has not shown obvious converge even though the settlement of pile top is greater near the ultimate load.When the pile group foundation is under applied loads,representing different construction stages,the pile-side soil of upper pile body generates larger excess pore water pressure dissipating with time gradually,which indicates that the soil consolidation process needs some time to be finished.Furthermore,the relationship between load-settlement of pile group shows apparent non-linear characteristics,and its P-S curve can be divided into three stages of linear phase,yielding stage and the overall destruction phase.In addition,the displacement rebound of pile group is small during unloading because the pile group generates large plastic deformation after the external load is applied.Therefore,the settlement of pile group foundation is one of the control conditions in the pile foundation design.