大直径钢管桩打桩振动对粘土土阻力的影响

随着海洋平台上部结构的增大,大直径超长的钢管桩越来越多的被应用于实际工程中.要想对桩的可打入性进行准确预测,首先要对打桩冲击振动对周围土体所造成的影响有准确的评价.为了对打桩过程中的土阻力作出准确分析,根据渤海海域36根桩的打桩记录,对其中粘性土土层的打桩记录进行了反分析,总结了打桩过程中粘土层中土阻力的变化特点,分析了这些特点产生的原因.同时利用实测数据回归得到粘土层强度衰减的规律,提出了进行打桩分析时粘土层计算参数选取的方法,并通过一个实际工程对此进行了验证.分析结果显示,粘土层在打桩过程受动力效应的影响较大,其土性参数会随着捶击数的增加而降低,采用回归结果对打桩预测可以取得较好的结果.

Influence of Pile Driving on Soil Resistance in Clay

With the increase of platform size,pipe piles with super large diameter and deep penetration are increasingly used in practice.In order to make accurate prediction of pile drivability,it is essential to evaluate the change of the soil properties under pile driving exactly,and it is the premise to predict the pile bearing capacity after pile driving.In order to learn more about the change of clay properties during pile driving,analysis on the pile driving record of 36 piles in Bohai area is conducted.According to the analysis,the soil resistance in the clay layers decreases as the depth increases,and it is very different from that in the sand layer.The FEM method is used to discuss the mechanism of this decrease.The back analysis is carried out to get more information.The results show that the clay properties are affected by the dynamic effect.The undrained shear strength of clay approximately decreases with the increase of thickness of the layer linearly.At the same time,a prediction is conducted based on results,and the result is closer to the pile driving record than that calculated by method normally used today.