现浇X形混凝土桩（X-sectional cast-in-place concrete pile，简称XCC桩）作为一种非圆截面异形桩，利用等截面异形周边扩大原理，将圆弧正拱变成反拱，达到扩大截面周长、提高承载力的目的。XCC桩安装过程其实是一个挤土过程，群桩沉桩挤土效应与单桩相比较为复杂，关于XCC桩群桩挤土效应方面的研究较少，而XCC桩群桩沉桩挤土效应是研究XCC桩的重要课题。基于透明土试验，开展了XCC桩与圆形桩群桩沉桩贯入试验，通过粒子图像处理技术获取沉桩过程的位移场变化规律，研究不同桩型和不同沉桩顺序对群桩沉桩挤土效应的影响。试验结果表明：对于最后贯入桩背桩面土的位移，XCC桩贯入引起的位移会比圆形桩率先达到峰值，XCC桩和圆形桩在群桩沉桩贯入过程中都会产生明显的累积效应和遮拦效应，且XCC桩的遮拦效应要强于圆形桩。最后，给出了XCC桩和圆形桩在不同沉桩顺序条件下群桩遮拦效应的经验公式。

X-section cast-in-place concrete pile (XCC pile), as a non-circular sectional special-shaped pile, turned the circular arch into reverse arch based on the principle of constant sectional special-shaped periphery enlargement, to turn the circular arc positive arch into an anti-arch, and finally forms a symmetrical X-shaped section, to expand the section perimeter and improve the bearing capacity. The installation process of XCC piles is actually a process of soil squeezing, and the effect of soil squeezing of pile group penetration is more complicated than that of single pile. However, there is limited research on the effect of soil squeezing of XCC piles group penetration at present, and the effect of soil squeezing of XCC pile group penetration is an important topic in the study of XCC piles. The effects of different pile types and different pile sequences on the squeezing effect of pile group penetration are studied. Based on the transparent soil technique, the penetration test of XCC pile and circular pile group was carried out. The displacement field variation pattern of pile group penetration was obtained via particle image velocimetry, and the influence of different pile types and penetration sequences on squeezing effect of pile group was studied. Results show that obvious cumulative effect and shielding effect can be observed during the penetration of XCC and circular group piles. For the displacement of the soil of the last penetrated pile dorsal surface, the displacement caused by XCC piles penetration reaches the peak first than that of the circular piles, and both XCC piles and round piles penetration produce obvious cumulative effect and shielding effect. The shielding effect of XCC pile is stronger than that of circular pile. Finally, empirical formula for predicting the shielding effect for XCC and circular piles under different penetration sequences was provided.

TU473.1

国家自然科学基金（51978105）；重庆市研究生科研创新项目（CYS22056）；重庆市杰出青年科学基金（cstc2021jcyj-jqX0017）