水下挤密砂桩沉桩过程动力特性*

挤密砂桩施工过程中，经常遇到硬夹层无法穿透、桩管爆裂等难题，采用灵敏度高、测试数据可靠性好的光纤光栅FBG传感器对打桩过程中桩身和桩端进行应力测试，并根据测试数据得出挤密砂桩沉桩过程不同土性条件下动侧壁摩阻力与地质勘探的静侧摩阻力、动端阻力与静端阻力的经验关系，对于打桩锤选型及进行可打性分析具有重要的指导意义。根据桩身应力监测结果得出，偏心作用是导致桩管爆裂的主要原因，在施工过程进行桩身垂直度控制具有重要意义。

Dynamic characteristics of underwater compaction sand pile

In the construction process of sand compaction pile,we often encounter the difficulties such as fail of penetrating through the hard interlayer and bursting of the pipe pile. Adopting the high-sensitivity & good- reliability test data of fiber grating FBG sensor to implement tress test for the pile body and pile end,we get to know the relationship between the dynamic side friction and static side friction,static resistance and static end resistance under different soil conditions during piling of the sand compacted pile,which is an important guidance for the selection of hammer type and feasibility analysis. According to the pile stress monitoring result,we know that the eccentric action is the main cause for the bursting of pipe pile. So,it is very important to control the verticality of the pile body during construction.