Horizontal Tensile Response And P-y Curve Characteristic Test Of Negative Inclined Pile Top

The engineering application of inclined pile is more and more extensive.Some scholars have studied the mechanical characteristics of inclined pile under horizontal load,but the tensile response characteristics under different inclined angles and pile bottom constraints are not very clear,which restricts the research on the working mechanism of inclined pile and the proposal of calculation methods.In this paper,inclined piles of 0°,10°,20° and rock-socketed 20° were set in the model sand,and horizontal pulling force was applied on the top of piles in the opposite direction to the inclined direction.The horizontal displacement,strain gauge and soil pressure box strain of 4 model piles were tested.The changes of pile horizontal displacement,bending moment,axial force,pile side friction,soil resistance,soil pressure and p-y curve characteristics with the change of inclination Angle and pile bottom constraint conditions are obtained.The results show that:(1)The maximum horizontal displacement of negative inclined pile is at the top of pile;In this model,the horizontal displacement mode of negative inclined pile in sand is "rotation+bending".There is a "zero displacement" in pile body.The horizontal displacement of pile body increases gradually with the increase of pile inclination Angle or the decrease of pile bottom constraint degree,while the "zero displacement" depth of pile body decreases gradually,that is,the horizontal bearing capacity of negative inclined pile decreases with the increase of pile inclination Angle or the decrease of pile bottom constraint degree.(2)When the negative inclined pile head is under active horizontal tension,the positive soil of pile body is uplifted due to compression,while the negative soil of pile body is depressed due to relaxation.(3)change with depth of negative inclined pile body bending curve shows "bow" type,central pile body is a maximum,and the maximum value with the increase of pile body tilt Angle or increase with the decrease of the pile bottom constraints,namely negative inclined pile with the increase of Angle or pile bottom constraint degree reducing,more and more easily in the central pile bending failure.(4)When the negative inclined pile is actively pulled horizontally,the maximum value of soil resistance at the pile side decreases with the increase of the pile tilt Angle or the increase of the constraint degree at the pile bottom.The soil resistance of the non-embedded pile is negative,while that of the embedded pile is positive.The maximum value of soil pressure on the side of each pile is at the bottom of the pile.The soil pressure above the bottom of the nonembedded pile is all negative,while the soil pressure on the embedded pile is all negative.(5)p/pub=[α(y/y50)]^β was used to fit the p-y curve of negative inclined pile.The parameters varied from 0.45 to 0.51,and the parameter β varied from 0.27 to 0.62.The inclination Angle and pile tip constraint have little effect on α,but the inclination Angle has little effect on the variation amplitude of β value.The variation amplitude of a and β value can be interpreted as the sensitivity of p-y curve parameters a and β to the influence of depth.The sensitivity of α and β decreases with the decrease of inclination Angle and the increase of pile tip constraint.