大直径超长管桩打桩过程中土塞性状研究

Study of influence of soil plug on driving for large diameter and deep penetration pipe piles

大直径超长桩的可打入分析是海洋平台打桩施工顺利进行的重要保障,土塞是否闭合的判断对于桩基可打入性分析具有较大的影响,因此,合理准确的土塞判断结果对提高桩的可打入分析的准确性具有重要的意义。以现场静力触探(CPTU)试验数据为依据,采用孔扩张理论推导了基于CPTU测试结果的桩端土的极限承载力计算公式;在求解桩端土体承载力时考虑了管桩与土体的刚度差异,同时考虑到打桩过程中的土体扰动。采用Randolph推荐的方法得到了土塞阻力,将两者进行比较,进而判断土塞的状态。通过实际工程的实测数据,对各个土层的土塞状况进行了判别,并根据判别情况采用波动方程的方法对桩基的可打入性进行了分析,将预测结果和现场的打桩记录进行了比较。计算结果显示,提出的方法与实测结果更为接近,有效地提高了桩的可打入性的预测精度。

Open-ended pipe piles are often used in offshore engineering. The drivability of large diameter and deep penetration piles is an important problem that many people are concerned with in practice,and is related to the response of the soil plug inside a pipe pile during pile driving. In this paper,firstly,the results of cone penetration test（ CPTU） is used to evaluate the bearing capacity of soil based on cavity expansion theory. Secondly,the frictional capacity of soil plug is calculated by the method proposed by Randolph.Finally,the soil bearing capacity is compared with plug capacity to decide whether the soil plug formed inside the piles is plugged or unplugged. According to the data from filed measurement,the soil plug state is evaluated by this method. The results show that it is in accordance with the actual situation.