土塞效应对PHC桩承载力的影响分析

Analysis about Bearing Capacity of PHC Pile Affected by Soil Plug

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,其计算值与试桩的结果往往相差较大。本文根据综合试桩的成果,分析了在粉、细砂地层中进入管桩内的土塞随着时间变化对端阻力的影响,在考虑土塞对端阻力前期的闭塞效应和后期的松弛效应的情况下,对桩端阻力进行了修正,所得到的承载力计算值与试桩结果较为吻合,通过本文的研究,建立了在粉、细砂地层中基于土塞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 （ pretensioned spun high strength concrete pile） shows the more complicated bearing mechanism. If the ultimate bearing capacity of single pile is calculated according to the empirical formula and modified formula in present code, the calculated value always has larger discrepancy with the result of the static loading test. Based on the result of pile test, the paper analyzes the influence to the bearing capacity of PHC pile toe effected by sandy soil plug with the time. On consideration of the prophase plugging effect and the anaphase slacking effect of the soil plug to the toe resistance, the calculated value of bearing capacity modified by toe resistance is close to the result of test. Based on the effect of sandy soil plug, the modified formula with CPT index to calculate the capacity of PHC pile has been established in the paper.