砂土中支盘桩抗压性能试验研究

支盘桩轴向受压过程是桩与周围土体相互作用的过程，研究支盘桩桩周土体的变形破坏机理对支盘桩竖向承载力的预测具有重要的意义。通过利用粒子图像测速技术进行了一系列的室内双支盘桩模型试验，对轴向荷载作用下支盘桩桩周土体变形特性进行非介入式测量。试验结果表明，不同相对密度下的荷载－位移曲线存在明显差异，相对密度增大可以大幅度提高双支盘桩竖向承载力并有效减小桩基沉降，密砂中双支盘桩的极限承载力是松砂的两倍以上。试验中发现支盘间距对支盘桩的竖向承载力有显著影响，随着盘间距的增加，支盘桩承载力增大但承载力增长率呈现出逐渐减小的趋势。针对地基土为密实砂土时，双支盘桩的支盘间距宜取盘径的３倍。

Experimental Study on Compressive Performance of the Branch Pile in Sandy Soil

The branch pile process of axial compression is the process of interaction between the pile and surrounding soil.The study on the deformation and failure mechanism of soil around the branch pile is of great significance for the prediction of vertical bearing capacity of the branch pile.A series of indoor model tests of the branch pile were carried out using particle image velocimetry(PIV)technology,and the deformation characteristics of soil around the supporting pile under axial load were measured by non-interventional method.The test results show that the load-displacement curves under different relative densities have obvious differences.Increasing the relative density of soil can greatly improve the vertical bearing capacity of the pile and effectively reduce the settlement of the pile foundation,the ultimate bearing capacity of the branch pile in dense sand is more than twice that of loose sand.It is found in the test that the distance between the supporting plates has a significant impact on the vertical bearing capacity of the pile,with the increase of plate spacing,the bearing capacity of the branch pile increases but the bearing capacity growth rate tends to decrease gradually.When the foundation soil is dense sandy soil,the plate spacing should be three times of the pile diameter.