基于土塞松弛效应的PHC管桩承载力修正公式

The Modified Formula of Bearing Capacity of PHC Pile Based on the Effect of Soil Plug Slack

开口管桩在沉桩过程中由于土塞的作用,其受力机理比闭口管桩更加复杂,根据现行规范中的经验公式以及修正公式计算单桩极限承载力,开口管桩的计算值常常低于或高于载荷试验的结果。而在砂土持力层中,由于砂土在沉桩过程中受到扰动,存在松弛效应,沉桩结束后土塞高度会发生变化,根据土塞的初始高度与松弛量,对桩端阻力进行修正,所得到的承载力计算值与载荷试验结果较为吻合,通过本文的研究,建立了基于土塞松弛效应下根据静力触探指标计算管桩承载力的修正公式。

Owing to the action of the soil plug in the process of driving pile, the open- end PHC- pile possesses the more complicated mechanism of bearing. The ultimate bearing capacity of single pile is calculated according to the empirical formula and modified formula in present code, the calculated value of open- end PHC- pile is always more or less than the result of the static loading test. The sandy soil will slack due to the disturbance of driving pile, and the height of soil plug will change in resting phase. According to the initial height and the slacking quantity of the soil plug, the calculated value of bearing capacity modified by toe resistance is close to the result of test. Based on the effect of soil plug slack, the paper established the modified formula with CPT index to calculate the capacity of PHC pile.