Numerical simulation of wave-current load on high pile cap foundation
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摘要: 为研究高桩承台基础在波流作用下的荷载时程特点和压力分布规律,开展某跨海大桥桩-承台复合基础的数值模拟研究。根据Stokes二阶波理论进行数值水池造波,采用雷诺平均应力方程(RANS)求解流体运动方程,计算得出3种淹没系数(0~1)下高桩承台基础的各部分水动力时程及其表面压力分布;应用流体体积函数(VOF)追踪液面形态模拟波浪形态时程。研究结果表明:(1)淹没系数较大时,承台水平力较大且主要来自波流联合作用,尾流区绕射波浪会产生负向水平力和负向浮托力,承台迎波面及顶面后方存在压力波动极值区;(2)随着淹没系数的降低,承台水平力减小,水平力主要以波浪拍击力为主,竖向浮托力、单桩水平力随之增加,尾流区绕射效应降低,承台压力极值波动区缩小直至消失;(3)桩基正向水平力最大值出现在边列最后排桩;负向水平力最大值出现在中列最后排桩。研究所得总力时程和压力分布规律可为优化结构设计提供参考。Abstract: In order to study the load time history characteristics and pressure distribution law of high pile cap foundation under wave current, the pile cap composite foundation of a sea crossing bridge is numerically simulated. According to Stokes second-order wave theory, wave generation in numerical pool is carried out, and Reynolds averaged Navier stokes equation (RANS) is used to solve the fluid motion equation. The hydrodynamic time history and surface pressure distribution of each part of high pile cap foundation under three submergence coefficients in the range of 0~1 are calculated. The volume of fluid function (VOF) is used to track the liquid surface shape and simulate the wave shape time history. The results show that: (1) When the submergence coefficient is large, the horizontal force of the cushion cap is large and mainly comes from the combined action of wave and current; the diffracted waves in the wake area will produce negative horizontal force and negative buoyancy force; there is an extreme pressure fluctuation region on the upstream and downstream of the cushion cap. (2) With the decrease of submergence coefficient, the horizontal force of cushion cap decreases, and the horizontal force is mainly wave beating force; the vertical buoyancy force and the horizontal force of single pile increase accordingly; the diffraction effect in the wake region is reduced; the fluctuation area of extreme pressure of bearing platform is reduced until it disappears. (3) The maximum positive horizontal force of the pile foundation appears in the last row of piles on the side column; the maximum negative horizontal force appears in the last row of piles in the middle column. The research on the total force history and pressure distribution law can provide a reference for optimizing structural design.
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Key words:
- wave current force /
- high pile cap /
- time history analysis /
- pressure distribution
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表 1 波浪要素及计算工况
Table 1. Wave elements and working conditions
淹没系数 静水深度/m 波高/m 周期/s 波长/m 静水流速/(m·s−1) Cs=1.00 22.30 6.9 8.3 96 3.64 Cs=0.55 18.93 Cs=0 14.80 表 2 不同网格方案参数
Table 2. Parameters of different grid schemes
最大网格尺寸/m 单元数/个 计算域范围 Z/Y向网格 X向网格 承台-桩表面网格 网格方案1 4 6 4 172 785 网格方案2 2 6 2 297 177 网格方案3 2 6 1 346 513 网格方案4 1 3 0.5 1 015 335 网格方案5 1 3 0.25 2 005 582 网格方案6 0.5 1 0.1 5 402 545 表 3
$ {C_{\text{s}}} $ =1.00计算结果对比Table 3. Comparison of calculation results (
$ {C_{\text{s}}} $ =1.00)单位:kN 方案 承台水平力 承台浮托力 桩基最大力 单桩最大力 网格方案1 7 296.22 3 154.68 5 698.01 741.48(Z8) 网格方案2 7 250.34 3 472.13 5 445.38 705.38(Z4) 网格方案3 6 993.28 3 766.94 4 876.31 540.78(Z10) 网格方案4 7 006.78 3 685.23 4 638.88 546.02(Z10) 网格方案5 7 182.15 4 206.10 4 461.20 556.40(Z3) 网格方案6 7 173.45 4 216.13 4 213.40 543.23(Z3) 试验数值 6 768.5 4 616.1 4 393.7 507.4(Z3) -
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