基于高频悬沙浓度观测的沉积物临界应力分析

Analysis of Critical Shear Stress for Sediments Based on High-Frequency Suspended Sediment Concentration Observations

关键词:  临界应力  悬沙浓度  再悬浮  底边界层  现场观测

Key words:  critical shear stress  suspended sediment concentration  resuspension  bottom boundary layer  field observation

摘要:

为了厘清不同水动力条件下沉积物临界应力状况，给沉积物输运模型提供关键的临界应力范围值，本研究基于山东半岛东岸黑泥湾海域布放的声学、光学等仪器现场连续观测34天水动力、底边界高频悬沙浓度的数据，利用浓度统计法量化研究了浪-流影响下沉积物再悬浮与沉降过程的临界应力。结果表明：底应力显著地响应浪-流的强迫，潮致底应力和浪致底应力的变化明显不同；观测期间发生60分钟以上的沉积物再悬浮事件共54次、沉降事件共55次；潮流占优情况下，粘性沉积物再悬浮临界应力变化范围为0.079-0.350 N/m2、平均值为0.208 N/m2，沉降临界应力变化范围为0.061-0.318 N/m2、平均值为0.188 N/m2；波浪占优阶段的临界应力较大，范围在0.895-4.666 N/m2，且随波浪强度变化一致。今后将浓度统计法估计临界应力推广到其他区域，从而丰富浅海区沉积物临界应力的空间分布。

Abstract:

This study aims to clarify the conditions of critical shear stress for sediments under varying hydrodynamic conditions, providing essential critical stress range values for sediment transport models. We conducted high-frequency hydrodynamic and suspended sediment concentration data over 34 days using acoustic and optical instruments deployed in the Heini Bay area off the eastern coast of the Shandong Peninsula. A statistical concentration method was used to quantify the critical shear stress associated with sediment resuspension and deposition under the influence of waves and currents. The results indicate that bottom shear stress responds significantly to the forcing of waves and currents, with distinct differences observed between tidal and wave-induced bottom shear stress variations. During the observation period, there were 54 resuspension and 55 deposition events lasting more than 60 min. Under conditions dominated by tidal currents, the range of critical shear stress for the resuspension of cohesive sediments was found to be between 0.079 and 0.350 N/m2, with an average of 0.208 N/m2, while the range for deposition critical shear stress was 0.061 to 0.318 N/m2, with an average of 0.188 N/m2. In contrast, during wave-dominated phases, the critical shear stress was significantly higher, ranging from 0.895 to 4.666 N/m2, and showed a consistent variation with wave intensity. Future research will extend the application of the statistical concentration method for estimating critical shear stress to other regions, thereby enhancing the understanding of the spatial distribution of critical shear stress in coastal seas.