静压桩施工过程中超孔隙水压力实例分析

Monitoring on Excessive Pore Water Pressure During the Precess of Static Pressing-in Pile

静压桩沉桩过程中超孔隙水压力会对周围环境造成影响。为了研究超孔隙水压力大小及随时间变化规律,结合工程实例进行超孔隙水压力监测试验,发现每天只观测一次孔隙水压力不能准确反映超孔隙水压力的变化规律;就单根桩而言,超孔隙水压力最大值出现在拔送桩筒至孔隙水压力计埋设深度处;超孔隙水压力随着离开桩的距离而衰减,其有效影响半径为15m左右;压桩速率可以通过其产生的孔隙水压力和上覆土层自重应力的比值来控制。

The excessive pore water presure may lead to the damage of surrouding civil works.For the purpose of avoiding these environmental effects,the excess pore water pressure monitoring tests were carried out in a practical construction.It is found that the once-a-day monitoring plan is not enough and will lost some peak values.In the procedure of a single pile pressing-in,the peak value comes into being when the actuator is pulled up to the elevation of pressure monitor.The excessive pore water pressure is dying out with the distance extending from the pressing-in pile,and the effective radius is about 15 meters.Finally,it is advised that the rate of pressing-in may be controlled by the ratio of pore water pressure versus the total stress in soil caused by its weight,so as to aviod the surrounding damage.