楔形管桩沉桩挤土效应试验研究

An Experimental Research on Soil Compacting Effect of Tapered Pipe Piles

为深入研究预应力混凝土楔形管桩在静力沉桩过程中的沉桩挤土效应,基于室内模型试验,对比分析直型管桩与楔形管桩在沉桩过程中挤土效应的差异,着重探讨楔角对楔形管桩沉桩特性的影响。结果表明:楔形管桩贯入阻力曲线呈斜“Z”型,直型管桩贯入阻力在沉桩中后期出现48.5%幅度的减小,楔形侧壁对土体的挤压效应是楔形管桩较大贯入阻力和较高竖向承载力的主要来源;无论径向还是竖向位移,沉桩前期楔形管桩位移较小,位移增长主要在中后期,挤土效应较直型管桩明显,而直型管桩沉桩过程中位移表现为先增大后减小,挤土范围小于一般桩体;楔形管桩桩身应变随沉桩深度和楔角的增加而增大,量值上远大于直型管桩;针对两种桩型“应力集中”现象出现的不同位置,对管桩桩身强度设计给出了建议。

In view of an inquiry into the soil compacting effect of prestressed concrete tapered pipe piles in the process of static pile driving,and based on the indoor model test,a comparison,as well as an analysis,has been made of the difference of soil compacting effect between straight pipe piles and tapered pipe piles in the process of pile driving,followed by an emphatic discussion of the influence of tapered angle on the pile sinking characteristics of tapered pipe piles.The results show that the penetration resistance curve of tapered pipe piles shows an inclined“Z”,and the penetration force of straight pipe piles decreases by 48.5%in the middle and later stage of pile sinking,with the squeezing effect of sloping sidewall on soil being the main source of the great penetration resistance and high vertical bearing capacity of tapered pipe pile;regardless of the radial or vertical displacement,the displacement of wedge-shaped pipe piles in the early stage of pile sinking is small,and the displacement increase is mainly in the middle and late stage.The soil squeezing effect is more obvious than that of straight pipe piles,while the displacement of straight pipe piles shows an initial increasing trend and a subsequent decreasing trend,with the soil squeezing range smaller than that of ordinary pile.The strain of wedge-shaped pipe piles increases with the increase of pile sinking depth and wedge angle,which is much larger than that of straight pipe piles.According to the different positions of the“stress concentration”of the two types of piles,some suggestions are given for the strength design of pipe piles.