加鳍桩抗扭性能及在推扭受荷群桩中应用

Torsional response of a pile with fins and its application in pile groups under combined lateral and torsional loads

加鳍桩是一种通过在桩身设置侧鳍片或在桩端设置尾鳍片以提高单桩抗扭能力的新型桩形式。圆截面单桩通过桩–土界面摩阻力提供扭转反力,单桩承载力一般较低。加鳍桩通过鳍片挤压土体,从而提升单桩扭转承载力。大尺度模型试验结果表明,桩身增加鳍片使单桩扭转曲线由陡降型变为缓变型,其抗扭刚度和承载力均有显著提高,在3.6°扭转角时扭转反力提高4.7倍。采用数值方法分析加鳍桩在水平偏心加载1×2群桩中的应用效果,分析表明,加鳍桩通过显著减小群桩扭转变形降低了两基桩间内力差异,明显降低群桩中基桩的最大剪力和弯矩,降幅分别达30%和79%,有效提高群桩抵御偏心加载能力。

A pile with fms is a newly developed pile foundation, which is capable of supporting large applied torques. The torsional resistance of the pile with fins is mainly supplied by the fins mounted along the pile shaft and at the bottom of the pile, which is quite different from a circular pile in the load transfer mechanism. Large-scale model tests are performed to investigate the differences between a circular pile and a pile with fins. It is found that the fins on a pile change the applied torque-twist angle curve from a steep drop type to a slow change type and improve the torsional resistance of the pile up to 4.7 times. To investigate the effect of piles with fins on pile groups subjected to eccentric lateral load, a 1 × 2 pile group with spacing of 3 times the diameter is analyzed using a sottware GROUP. It is found from the numerical results that the maximum pile-head torsion and bending moment decrease by 30% and 79% respectively as the piles with fins are employed in the group.