刚性单桩竖向循环加载模型试验研究

Experimental investigation on a single stiff pile subjected to long-term axial cyclic loading

刚性桩在高铁低矮路堤加固中广泛应用。利用浙江大学大型地基与边坡工程模型试验系统,开展了饱和粉土地基中刚性单桩动力加载大比例模型试验,对不同静偏荷载及循环荷载组合作用下的桩基性状进行了研究。通过模型桩身安装的各类传感器,对桩顶累积沉降、桩身轴力、桩–土界面孔压及正应力变化进行了监测。试验发现,循环剪切会引起桩–土界面土颗粒重排,导致桩–土界面孔压及有效应力状态发生改变。循环荷载比CLR对桩基累积沉降、桩侧应力状态发展影响显著。根据试验结果,对累积沉降发展规律进行了归纳,分析并讨论了桩侧应力状态变化机理。

Stiff pile-supported low embankments have been widely adopted in high-speed railway lines in China.Large-scale model tests are carried out to investigate the response of a single stiff pile subjected to axial dynamic loading in silts.Tests are conducted by means of the large foundation and slope engineering simulation system in Zhejiang University.Various combinations of static and cyclic loadings are applied in tests.The pile used in the tests are instrumented with load cells,pore pressure probes and pressure cells.The accumulated settlement,axial force,pore pressure and radial total stress along the pile are monitored.The test results indicate that the cyclic loading causes soil particle rearrangement,which leads to a change in stress state at soil-pile interface.The accumulated settlement and stresses acting on pile shaft are greatly influenced by the cyclic loading ratio（CLR）.The development of the accumulated settlement with different CLRs is summarized and presented.The possible mechanisms responsible for stress changes at soil-pile interface are discussed.