Vertical structure of pore pressure under surface gravity waves on a steep, megatidal, mixed sand‐gravel‐cobble beach
Vertical structure of pore pressure under surface gravity waves on a steep, megatidal, mixed sand‐gravel‐cobble beach
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陡峭大潮汐砂砾石卵石混合海滩表面重力波下孔隙压力的垂直结构
DOI：
10.1002/2016jc012257
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发表时间：
2017
影响因子：
--
通讯作者：
A. Hay
中科院分区：
文献类型：
--
作者：
T. Guest;A. Hay
研究了天然、陡坡、巨潮、沙砾卵石混合海滩的潮间带内表面重力波引起的孔隙压力的垂直结构。埋藏孔隙压力传感器的相干垂直阵列的结果以信号相位滞后和衰减的形式呈现，作为振荡强迫频率和埋藏深度的函数。将观测结果与理论多孔弹性床响应模型的预测进行比较表明，观测到的大相位滞后和衰减可归因于间隙截留的空气。除了对截留空气体积的依赖性之外，孔隙压力相位和衰减还对沉积物的导水率、潮汐周期期间平均水深的变化以及风暴事件期间高能波浪作用引起的海滩表面物质的重新分布/重新排列敏感。后一个结果表明，仪器埋藏期间沉积物柱扰动对孔隙压力的影响可能持续数天至数周，具体取决于波浪强迫条件。总而言之，这些结果对使用孔隙压力测量来估计陡峭的混合砂砾海滩上表面重力波的运动学特性的实用性提出了严重的问题。
The vertical structure of surface gravity wave-induced pore pressure is investigated within the intertidal zone of a natural, steeply sloping, megatidal, mixed sand-gravel-cobble beach. Results from a coherent vertical array of buried pore pressure sensors are presented in terms of signal phase lag and attenuation as functions of oscillatory forcing frequency and burial depth. Comparison of the observations with the predictions of a theoretical poro-elastic bed response model indicates that the large observed phase lags and attenuation are attributable to interstitial trapped air. In addition to the dependence on entrapped air volume, the pore pressure phase and attenuation are shown to be sensitive to the hydraulic conductivity of the sediment, to the changing mean water depth during the tidal cycle, and to the redistribution/rearrangement of beach face material by energetic wave action during storm events. The latter result indicates that the effects on pore pressure of sediment column disturbance during instrument burial can persist for days to weeks, depending upon wave forcing conditions. Taken together, these results raise serious questions as to the practicality of using pore pressure measurements to estimate the kinematic properties of surface gravity waves on steep, mixed sand-gravel beaches.