Silt and silty sand are widely distributed in the alluvial plain of the Yellow River in China.The Tianjin-Weifang high speed railway bridge passing through this area extensively uses prestressed high intensity concrete(PHC)pipe piles with a diameter of 1 m.The horizontal bearing characteristics of large diameter pipe piles in this stratum are unknown,and the proportional coefficient m of the key design parameter horizontal foundation coefficient is unclear,which affects the economic and safety design of high speed railway bridge pile foundations.Horizontal static load tests were conducted on two large diameter pipe piles in areas with deep loess and silty sand using the slow maintenance load method.The results show that with the horizontal critical load as the boundary point,the horizontal displacement of the pile top changes from approximately linear growth to nonlinear growth with the increase of load,and the soil around the pile transitions from elastic to plastic state,with the plastic zone continuously expanding.As the horizontal load on the pile top increases,the bending moment of the pile also increases accordingly,and the maximum bending moment occurs 3～4 m below the point of horizontal load.The comprehensive m value of the silt and silty sand layers decays with a power function as the horizontal displacement increases.After considering the work reduction coefficient,the m value is taken as 5.536 MN/m4.
large diameter PHC pipe pilehorizontal static loading testbearing characteristicm valueinternal force of pile
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