中文摘要：

现浇x形桩（以下简称XCC桩）是近几年提出的一种新型异形截面桩，其沉桩挤土效应不同于传统圆形截面桩。针对目前的理论模型和试验技术对于研究异形截面桩沉桩挤土效应的不适用性，提出一种新的异形截面桩沉桩模型试验技术。基于透明土变形可视化技术，分别研究了圆形桩和XCC桩沉桩挤土的位移场变化规律。通过将圆形桩透明土沉桩挤土位移场的结果跟传统的理论模型（圆孔扩张法和应变路径法）进行对比，验证了透明土沉桩模型试验技术的可靠性。随后，开展XCC桩的沉桩挤土试验。进一步地，基于模型试验结果提出一种简单的修正扩孔理论用于计算XCC桩异形桩的沉桩挤土径向位移的分布规律，并将理论计算位移与模型试验测量值进行对比验证修正扩孔理论的合理性。提出的异形桩透明土沉桩模型试验技术以及修正扩孔理论可以作为研究其他如矩形桩、Y形桩、H形桩等异形截面桩的沉桩挤土效应问题的一个基础。

英文摘要：

X-section cast-in-place pile （XCC pile） is a new developed type of non-cylindrical cross section pile recently, whose penetration effect of XCC pile is different from the conventional circular cross section pile. Since the existing theoretical model and test technique are not suitable for investigating the non-cylindrical cross section pile, a new mode test technique is presented. Based on the deformation visualization technique of transparent soil, the soil displacement of the circular pile and XCC pile is investigated, respectively. The transparent soil model test technique is validated by comparing the test results of the circular pile with the theoretical prediction （ cylindrical cavity expansion and strain path method）. Subsequently, the XCC pile penetration test is conducted. Furthermore, a simple modified cavity expansion model is proposed to compute the radial displacement induced by the pile penetration, and the theoretical predictions are compared with the measured values to validate the modified cavity expansion model. The presented model test technique for the non-cylindrical pile and the modified cavity expansion mode can provide the theoretical base for investigating other non- cylindrical piles such as rectangular, Y-shaped and H-shaped cross section piles.