斜向抗拔螺旋群桩基础承载性状试验研究

通过3桩等边三角形承台原型群桩基础的4次斜向抗拔、2次垂直抗拔和5次单桩垂直抗拔试验,绘制了相应的荷载位移关系曲线。依据地基变形特点和曲线变化特征,建议采用具有明确物理特征的H-(△x/△H)曲线判定螺旋群桩基础水平方向极限荷载,垂直方向抗拔极限荷载依据单位荷载的桩顶位移变化率、桩顶位移增量以及地基变形特征判定,并讨论了群桩基础在斜向荷载和垂直荷载上拔过程中的群桩效率。试验表明:抗拔群桩基础的群桩效率与外荷载的作用角度有关,斜向抗拔螺旋群桩基础的群桩效率小于垂直抗拔群桩基础的群桩效率,荷载水平分量加快了该种群桩基础的上拔破坏,斜向抗拔群桩的极限破坏荷载和极限位移要小于垂直抗拔螺旋群桩基础。

Bearing capacity of screw pile group determined by inclined pull-out test

Through 4 times of inclined pull-out field tests and 2 times of vertical pull-out field tests on a pile group with 3 piles composing an equilateral triangle in plane,and 5 times of vertical pull-out field tests on a screw pile,some curves of load and settlement were drawn.On the basis of the characteristics of ground deformation and the above curves,the horizontal and vertical ultimate loads were respectively estimated by the H-(Δx/ΔH) curve and the composed method of the ratio of displacement to unite load,the incremental displacement of pile head,the characteristics of ground deformation,and the group efficiency were analyzed for the screw pile group under inclined and vertical loads.It is shown that,the group efficiency of pile group is related to the working angle of load,the pull failure of the pile group is quickened by the horizontal component of force,and the ultimate load and displacement of pile group under inclined pull-out load are less than those under vertical pull-out load.