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挤土型桩的挤土效应一直是工程界研究和关注的热点问题之一。结合南京长江四桥北接线段现浇X形桩软基处理工程,首次开展现浇X形混凝土桩(简称X形桩)沉桩过程现场试验,测得不同X形横截面方向、不同距离及深度处的水平位移、侧向土压力以及孔隙水压力的分布规律,研究X形桩挤土效应规律。研究结果表明,最大水平位移发生在桩顶,距离5倍等效桩径处的土体水平位移可以忽略不计;随着桩中心距的增加,挤土压力和孔隙水压力逐渐减小,并且尖角方向的挤土压力大于凹弧方向的挤土压力。现场试验数据为X形桩的布置形式以及桩间距的选择提供有力的设计参考依据。
The squeezing effect of soil compaction pile has always been one of the hot issues in engineering research and attention. Combined with the on-site X-shaped pile soft foundation treatment project in the north section of Nanjing No.4 Bridge, the field test of pile pouring process of X-shaped cast-in-situ concrete piles was conducted for the first time. The direction, The depth of the horizontal displacement, lateral pressure and pore water pressure distribution law to study X-shaped pile squeezing effect law. The results show that the maximum horizontal displacement occurs at the top of the pile, and the horizontal displacement of the soil at the equivalent pile diameter of 5 times of the pile diameter is negligible. With the increase of pile center distance, the squeezing pressure and pore water pressure gradually decrease, The squeezing pressure in the direction of the angle is greater than the squeezing pressure in the direction of the concave arc. Field test data provide a powerful reference for designing the layout of X-shaped piles and the choice of pile spacing.