静压桩承载性能的分析研究

本文在总结静压桩基础在广东应用经验的基础上,讨论了静压桩基础的成桩机理,压桩时穿过土层的滑动摩擦力一般较小且在同一土层中不随入土深度的增加而累计增大,压桩阻力随桩端处土体的软硬程度即桩端处土体的抗冲剪阻力的大小而波动,压桩停止后,随着超孔隙水压力的消散,滑动摩擦力逐渐转化为静摩擦力,从而使静压桩的承载力得到恢复。通过对241根桩的试验检测资料,研究分析了静压桩施工终压力和极限承载力的区别和关系,根据桩的人土深度,简易地将桩划分为短桩、中长桩和长桩,并认为短桩的极限承载力将小于压桩的终压力,而长桩的极限承载力将大于终压力。提出了静压桩适用的承载力估算的经验公式,同时给出了静压桩设计的极限侧摩擦力标准值和极限端阻力标准值的参考表。

Research on bearing capacity mechanism of statically pressed precast concrete piles

The bearing capacity mechanism of statically pressed precast concrete piles was discussed based on the application experience of pile foundation in Guangdong province. The mechanism was as follows: at the period of pile pressing, the sliding-friction force between pile and soil was rather small, it would not accumulate and increase with the embedded depth of pile in the same soil layer, the main resistance against the pressing force was the punching strength of the soil layer where the pile rested; as the pressing process was finished, the bearing capacity of the pile would berestored along with the disappearance of the pore water pressure and change of static friction force from sliding friction force. Based on the test data of 241 piles, the difference and relationship between the final pressure acting on pile top and the ultimate bearing capacity of the statically pressed piles was analyzed. It was shown that these piles could be classified as short pile, middle pile and long pile according to their embedded depth; the ultimate capacity of short pile was less than the final pressure, while the ultimate capacity of long pile was larger than the final pressure. Empirical formulas for estimating the adaptable bearing capacities of such piles are presented, and the referencial tables of standard values of ultimate side resistance and ultimate end resistance are listed as well.