涌潮水流作用下桩柱表面压强及受力分析

Analysis of the Surface Pressure and Force of Piles Under Tidal Bore

涌潮水流是一种蕴含较大能量的强非线性间断流.针对我国钱塘江河口地区范围内桥墩等桩式建筑物在涌潮水流作用下长期遭受的猛烈冲击问题,采用物理模型试验对桩柱在潮前水深上下两部分表面压强时程变化及涌潮潮头最大冲击压强出现位置进行了探讨并拟合得到最大冲击压强计算公式;采用数值模拟手段进行分离式建模,对桩柱在潮前水深上下两部分受力进行提取分析并拟合得到涌潮作用力计算公式.研究结果表明,涌潮水流与桩柱相互作用过程可分为3个阶段:在瞬时冲击期内,潮前水深以上桩柱部分在潮头猛烈冲击作用下,桩柱表面压强及受到的作用力瞬间增大至极大值,潮前水深以下部分表面压强和受到的作用力增长缓慢;衰减振荡期内,桩柱在潮前水深以上部分表面压强和受到的作用力迅速下降,潮前水深以下部分压强波动不大,受到的作用力衰减速率明显小于潮前水深以上部分;绕流作用期内,桩柱在潮前水深上下两部分表面压强和受力波动逐渐减小.桩柱在涌潮作用下表面压强及受力大小与涌潮水流参数中的潮前水深h0和落潮流速V0呈负相关,与涌潮高度H呈正相关;涌潮作用下最大冲击压强出现在0.5 H附近,拟合得到的最大冲击压强及作用力计算公式经验证后具有良好的精度,可为相关应用提供参考.

The tidal bore is a kind of strong nonlinear discontinuous flow containing large energy.Aiming at the long-term violent impact of pile-type buildings,such as bridge piers,in the Qiantang River estuary area of China under tidal bore,the physical test model is used to test the time-history variation of the surface pressure of piles in the upper and lower parts of the tidal water depth and tidal velocity.The position of the maximum impact pressure of the head is determined and fitted to obtain the formula for calculating the maximum impact pressure.The numerical simulation is used to separate the models of the upper and lower parts of the pile before the tide.The force is separately extracted,analyzed,and fitted to obtain the formula for calculating the tidal force.Results show that the interaction process between the tidal bore and the pile can be divided into three stages.Under the impact of the water depth before the tidal bore,the surface pressure of the pile and the force received will increase instantaneously under the impact of the tide.In terms of the maximum value,the surface pressure and force affected by the water depth before the tide slowly increase.During the attenuated oscillation period,the surface pressure and force received by the pile before the tide rapidly decrease.Moreover,the pressure below the tide depth does not fluctuate.The rate of force attenuation is significantly smaller than that of the pre-tidal water depth.During the flow period,the surface pressure and stress fluctuations of the piles in the upper and lower parts of the tidal water depth gradually decrease.The surface pressure and force under tidal action are negatively correlated with the pre-tidal water depth h0 and falling tide velocity V0 and positively correlated with the tidal height H.The maximum impact pressure under tidal action occurs near 0.5 H.The maximum impact pressure and force calculation formula obtained after fitting have good accuracy and can provide a reference for related applications.