大直径管桩沉桩过程中溜桩判断方法研究

海洋工程中大直径管桩沉桩过程中常会出现溜桩现象,未经预料的溜桩会引起很多严重的工程问题,有必要对溜桩段进行准确判断。结合实际工程对溜桩产生及停止的机制进行分析;通过研究沉桩过程中桩周土体强度折减及超孔压的作用,提出动贯入阻力的计算方法;利用功、能原理对溜桩过程中所发生的能量转化进行分析,并推导相应计算公式,结合动贯入阻力计算方法,实现对溜桩过程的预测。结果表明,当桩端进入深厚砂土层或动侧摩阻力达到一定值时溜桩将逐渐停止,若是后者则再次打桩后不再发生溜桩现象。计算动侧摩阻时须考虑沉桩过程中扩孔效应和循环荷载作用。计算结果与现场实测数据吻合较好。

Research on prediction of pile running during large diameter pipe piles driving

In ocean engineering, pile running often occurs during the driving process of large diameter pipe piles. Unpredicted pile running will cause severe consiquences, so an accurate prediction is necessary. The generating and stopping mechanisms of pile running in practical engineering were analyzed. The computing method of dynamic resistance was proposed by researching the strength reduction of soil and the excess pore pressure around the pile. Using the principle of work and power, the transformation of energy was analyzed during pile driving, and the corresponding equations were derived. Combining with the computing method of dynamic resistance, the prediction for the process of pile running was realized. It turns out that the pile running will stop when the pile tip goes into a thick layer of sand or the skin friction reaches a certain high value. If the later situation occurs, the pile running won ''t happen again. When calculating the skin friction, the effects of pore expansion and cyclic loading must be considered. The calculated results agree well with the measured ones.