中文摘要：

海工环境中水平承载PHC管桩在氯离子的侵蚀作用下承载性能会逐步下降。通过分析氯离子扩散机理、钢筋锈蚀机理，得到PHC管桩中钢筋的初锈时间；通过与单、双面配筋矩形受弯构件的锈蚀机理类比，推导出考虑钢筋锈蚀的PHC管桩抗弯刚度计算公式，求得PHC管桩水平承载力丧失时间；结合单桩水平承载力弹塑性理论，进一步建立PHC管桩水平承载寿命预测模型。分析发现PHC管桩在海工环境下水平承载寿命经历明显的三个阶段，即由氯离子开始扩散至钢筋初锈阶段、承载力缓慢下降阶段和桩体崩塌阶段。PHC管桩水平承载寿命较短的主要原因是钢筋的直径和保护层厚度较小，此外环境温度、临界氯离子含量和桩型也会对其产生重要的影响。提出以钢筋锈蚀率达到10％的时间作为受腐蚀情况下PHC管桩水平承载的极限寿命。

英文摘要：

Horizontal bearing capacity of PHC pipe pile gradually decreases due to chloride ion penetration in marine environments. The initiation time of steel corrosion in PHC pipe pile was attained based on chloride ion diffusion and steel corrosion mechanism. The calculation formula of bending stiffness of PHC pipe pile was derived by analogy with the corrosion mechanism of rectangular reinforced concrete beams, and the degradation time of horizontal bearing capacity was predicted. By combining the elastic-plastic theory for horizontal bearing capacity of single pile, the service life prediction model of PHC pipe pile was established. Based on the calculations and analyses, it shows that the service life of horizontal bearing capacity of PHC pipe pile in marine environments experiences three stages, namely, the stage from chloride ion diffusion to initiation of steel corrosion, the bearing capacity degradation stage and the pile collapse stage. The short service life of horizontal bearing capacity of PHC pipe pile is mainly attributed to the small steel diameter and thin protective layer. In addition, environment temperature, critical chloride ion content and pile types are also important influencing factors. Furthermore, it is proposed that the time when the steel corrosion rate reaches 10% may be viewed as the limit service life of horizontal bearing capacity of PHC pipe pile.