填芯PHC管桩桩身抗压承载力试验与理论计算方法研究

Study on experiment and theoretical calculation method of compressive bearing capacity of filled PHC pipe piles

为了考察竖向极限荷载作用下填芯管桩的力学性能,开展了填芯PHC管桩桩身的室内模型试验研究。提出了不考虑与考虑混凝土残留预压应力影响以及不考虑与考虑桩身配筋作用下的填芯PHC管桩桩身抗压承载力的修正理论计算公式。通过对空心、素混凝土填芯、钢筋混凝土填芯PHC管桩桩身抗压承载力的试验与理论计算研究,得出如下结论:填芯PHC管桩的桩身抗压承载力设计值的计算结果与其实测结果之比介于59.9%~93.8%之间,计算结果普遍小于实测结果,说明理论计算公式偏于安全;不考虑混凝土残留预压应力但考虑桩身配筋作用时,桩身抗压承载力设计值的理论计算结果与试验结果最接近;采用不考虑混凝土残留预压应力和桩身配筋作用的理论公式计算填芯PHC管桩桩身抗压承载力设计值是安全、适用的;填芯能够在一定程度上提高PHC管桩的桩身抗压承载力,钢筋混凝土填芯对PHC管桩桩身抗压承载力的增强效果好于素混凝土填芯;直径大于1 000mm的PHC管桩填芯后其桩身抗压承载力提高50%以上,随着PHC管桩直径的增大,填芯对PHC管桩桩身抗压承载力的贡献也进一步增大。

In order to investigate the mechanical properties of filled pipe piles under the action of the vertical ultimate load,the research was carried out on indoor model test of PHC pile filled with concrete core. The corrected theoretical formulas of axial compressive bearing capacity of PHC pile filled with concrete core were proposed considering concrete residual compressive pre-stress effect and pile reinforcement effect or not. By the comparative analysis between the compressive bearing capacity experimental values and its corresponding theoretical calculation values of PHC pipe piles and PHC pipe piles filled with concrete core or reinforced concrete core,it suggests that the ratios of the calculation compressive bearing capacity design value and its test value are between 59. 9% to 93. 8%,most of the calculated values are less than the measured values which indicates the safety of theoretical formula. In the case of not considering the residual pre-stress but considering the role of concrete pile reinforcement effect,the theoretical calculation result is the most close to the test result of vertical compressive bearing capacity design value of filled PHC pipe piles. The calculation formula not considering the residual pre-stress and concrete pile reinforcement is used to calculate the design value of vertical compressive bearing capacity of filled PHC pipe piles,which is safe and applicable. The filling core is helpful to improve the compressive bearing capacity of PHC pipe piles to a certain extent,and the compressive bearing capacity of PHC pipe piles filled with reinforced concrete core is better than that of plain concrete core. The bearing capacity of PHC pipe piles diameter is greater than 1 000 mm filled with concrete core increases by more than 50%. Moreover,with the increase of PHC pipe piles diameter,the contribution of filling core to compressive bearing capacity of PHC pipe piles further increases.