Surcharge loading, phreatic level decline and other factors cause negative skin friction on the peripheral surface of piles, which increases engineering insecurity. Negative skin friction has been researched deeply by filed, scale and numerical test. However, few studies have considered the influences of drainage boundary conditions on pile settlement considering consolidation of surrounding soils. Based on 1D perfect elasto-plastic model, this paper demonstrates that pile-soil elastic relative displacement at the position of neutral point is zero, and derives a simplified settlement calculation method. Calculation results show that change of neutral point position makes the pile-soil relative displacement not zero. Finally, the proposed method is verified by FEM method and used to analyze the influence of different drainage cases on the pile settlement.

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