珊瑚砂地基中膨胀混凝土桩竖向受压承载性能研究

为研究珊瑚砂地基下膨胀混凝土桩竖向承载特性，开展了室内单桩竖向静载模型试验，分析了膨胀混凝土桩的单桩荷载-位移曲线以及轴力、桩侧摩阻力等沿桩长分布特性，与PLAXIS 3D软件数值模拟结果进行对比并探究了线膨胀率对承载特性的影响。结果表明：珊瑚砂中膨胀混凝土桩的荷载位移曲线呈现缓变型，在加载过程中，荷载主要由桩侧摩阻力承担，轴力随着深度的增加而减小，桩侧摩阻力随深度先增加后逐渐减小，随荷载的增加逐渐发挥作用。随着膨胀剂用量的增加，桩身线膨胀量逐渐增加，桩-土相互作用更加明显。添加25% HCSA型膨胀剂可提高近20%的极限承载力和56%的极限侧阻力，提高桩体线膨胀率可以有效提高桩的极限承载力和侧摩阻力。该研究可为珊瑚砂桩基工程设计提供参考。

A study of vertical bearing capacity of expansive concrete pile in coral sand foundation

To investigate the vertical bearing characteristics of expansive concrete piles embedded in coral sand foundation, the vertical static load test of single model pile was carried out in laboratory. The load-settlement curve, axial force and frictional resistance of single expansive concrete pile were analyzed, and compared with the numerical results from PLAXIS 3D software simulation. The effect of the linear expansion rates was discussed. The results show that the load-displacement curves of expansive concrete piles in coral sand show a slow change. During the loading process, the load is mainly borne by the side friction resistance of the pile. The axial force decreases with the increase of the depth, and the side friction resistance of the pile first increases with the depth and then gradually decreases, and gradually plays a role as the load increases. With the increase of expansive agent dosage, the linear expansion of pile shaft increases gradually and the pile-soil interaction becomes more obvious. Adding 25% HCSA expansive agent can increase the ultimate bearing capacity by nearly 20% and the ultimate value of pile side friction by 56%. Increasing the linear expansion rate of the pile can effectively increase the ultimate bearing capacity and side friction resistance of the pile. This study provides a reference for the pile foundation projects in calcareous sand foundation.