大直径超长灌注桩荷载传递机理的自平衡试验研究

杭州湾跨海大桥南航道主墩(D13)基础采用直径2.8m、长120m的钻孔灌注桩。其中两根试桩采用四回路U形管压浆工艺进行桩端压浆,并在压浆前后分别应用自平衡测试法进行静载试验。通过对试验数据采集整理,从荷载-沉降关系、桩侧摩阻力分布及其与桩土间相对位移关系、桩端阻力发挥等方面,分析了该类超长桩荷载传递机理的某些特征和承载特性。结果表明,桩端压浆可以最大限度地减小施工造成的不利影响,改善超长桩荷载传递性能,大幅提高该类桩承载性能的稳定性。

Experimental research on the load transfer mechanism of super-long large diameter bored pile with the self-balanced load test method

The bored piles 2.8 m in diameter and 120 m in length were adopted in the foundation of DI3 frusta under a bridge. 4-loop and U-size-grouting-pipe procedure was applied on two test piles, and static load tests were carded out on these two piles with the self-balanced load test method. Through collecting and dealing with the experimental data, some characteristics of load transfer mechanism and bearing behavior of bored pile, such as the relationship between load and settlement, the distribution of shaft friction, the relationship between pile-soil relative displacement and shaft friction, and tip resistance behavior were analyzed. It was indicated that, tip grouting could greatly decrease the disadvantageous construction influence, improve the load transfer mechanism of super-long bored pile, and greatly increase the stability of beating behavior.