欠固结土中嵌岩斜桩弯矩及负摩阻力模型试验研究

Model-experimental study on bending moment and negative skin friction of rock-socketed inclined pile in underconsolidated soil

嵌岩斜桩是海上风电系统、港口高桩码头等设施常用的基础结构。嵌岩斜桩在穿越深厚软土层时,土体固结沉降不可避免地影响桩身轴力和弯矩的分布,威胁桩体安全。针对穿越深厚软土层的嵌岩斜桩开展了室内模型试验研究,对5根不同倾角和直径的模型桩进行试验,通过较长时间地监测土层固结沉降下的桩体应变,分析了固结时间、倾角、桩径等因素对桩身轴力、桩身中性点位置、桩侧负摩阻力、桩身弯矩等分布规律的影响。结果表明:嵌岩斜桩的负摩阻力、轴力及弯矩的发展都具有明显的时间效应;随时间、倾角的增加,桩侧中性点轴力及桩身弯矩峰值均增加,同时中性点上移、弯矩峰值点下移,最终中性点稳定于岩层上部0.1倍土层深度,弯矩峰值点稳定于岩-土界面处。

Rock-socketed inclined pile is a common foundation structure for offshore wind power system and high-pile wharf.When rock-socketed inclined pile passes through deep soft soil,the consolidation settlement of soil inevitably affects the distribution of axial force and bending moment of the pile body and threatens the safety of it.An indoor model-experimental study is carried out herein on the rock-socketed inclined pile crossing deep soft soil,in which the experiments are made on five model-piles with different inclination angles and diameters.Through long-term monitoring of the strain of the pile body under the soil consolidation settlement,the effects of the factors such as consolidation time,inclination angle,pile diameter etc.on the distribution laws of pile axial force,pile neutral point position,pile side negative skin friction,pile bending moment,etc.are analyzed.The results show that all the developments of the negative skin friction,the axial force and the bending moment of the rock-socketed inclined pile have obvious time effect.Both the axial force of the pile neutral point and the peak value of the pile bending moment are to be increased along with the increases of time and inclination angle,meanwhile,the neutral point moves up and the peak bending moment moves down,and finally the neutral point stabilizes at the position of 0.1 times the depth of soil layer in the upper part of rock stratum and the peak bending moment stabilizes at rock-soil interface.