【作者】 郑杰文；

【导师】 贾永刚；

【作者基本信息】 中国海洋大学 ， 环境工程， 2013， 博士

【摘要】 海洋动力作用下现代黄河三角洲沉积物再悬浮对于黄河入海泥沙远距离输运及其命运归宿的解读具有重要作用。目前对于沉积物再悬浮过程及其动力发生机制的研究更多关注于浪、流边界层的相互作用，往往忽略底床沉积物内部发生的一系列动力响应过程对其再悬浮的影响，从而制约了现代沉积动力过程研究的深入。本学位论文在国家自然科学基金风暴对黄河三角洲侵蚀控制与海床液化（资助号：41072215；时间：2011-2013）与黄河口侵蚀再悬浮物海床内部输供及控制因素研究（资助号：41272316；时间：2013-2016）资助下，研究了现代黄河三角洲沉积物波浪动力响应过程对海底沉积物再悬浮的控制作用。本论文基于室内动三轴试验、现场造波试验与室内波浪水槽试验，研究了现代黄河三角洲沉积物波浪动力响应过程；基于现场原位观测与室内水槽试验，研究了海洋动力作用下现代黄河三角洲沉积物再悬浮过程；基于现场调查与现场试坑试验，研究了现代黄河三角洲沉积物再悬浮特性的时空分布特征及动态变化规律；基于室内动三轴与冲刷水槽模拟试验、现场造波与循环水槽试验，及数理统计与理论计算，研究了波浪对现代黄河三角洲沉积物再悬浮的控制机理。取得的主要研究成果主要有以下几方面：（1）50年一遇极端海况下，现代黄河三角洲不同沉积区域埋深4m沉积物均发生孔压累积，其中沉积年代老的沉积区域主要表现为缓慢增长快速增长至上覆有效应力，沉积年代新的区域表现为快速增长缓慢增长稳定于不足上覆有效应力50%的定值；孔压累积模式普遍符合对数曲线增长模型，对于沉积年代较老与沉积年代最新的沉积物而言，适用性相对较差；大风浪作用下，表层30cm深度范围内沉积物孔隙水压力普遍呈现出累积升高剧烈振动缓慢消散的发展模式，孔压累积导致底床内部细粒物质向上输运，使底床发生“粗化”，原状潮滩沉积物沉积年代越老，沉积物级配越差，“粗化”能力越强。（2）在近岸海区强风浪条件下，若底床沉积物内孔隙水压力累积程度很小，底床发生小再悬浮事件，波致剪切力为其显著动力发生机制；若底床沉积物内孔隙水压力累积程度很高，底床发生大再悬浮事件，波致沉积物液化为其显著动力发生机制；波浪作用下底床内部细粒物质向上输运进而发生再悬浮最高可达总悬浮量的50%。（3）现代黄河三角洲潮滩沉积物再悬浮特性存在不同时空尺度的分布特征及动态变化规律；与高潮滩与中潮滩沉积物相比，低潮滩沉积物易发生再悬浮，受海洋动力作用影响显著，空间非均匀分布程度高；北部与南部潮滩沉积物易发生再悬浮，东部与东北部不易发生再悬浮；在海洋动力作用下，初始堆积沉积物3⁴天即与原状潮滩沉积物表现出相近的再悬浮特性；现代黄河三角洲沉积物的再悬浮特性在百年的沉积历史中表现为先增长后降低的演变趋势。（4）大幅值波浪荷载作用可引起沉积物临界剪切应力与起动流速的线性衰减，此过程与波浪荷载作用下沉积物结构强度的损失密切相关；较小幅值波浪荷载作用初期，沉积物临界剪切应力与起动流速显著降低，之后在波动中趋于稳定；沉积物孔压累积引起沉积物的软化过程是波浪荷载作用下其再悬浮特性显著降低的重要因素，波致沉积物粒度成分的动态变化是引起波浪荷载作用后期再悬浮特性变化的重要因素；基于本文建立的数学模型得出，现代黄河三角洲埕岛海域5⁵0年重现期波浪要素下的海床内部沉积物再悬浮通量约为17⁹1g·m^-2·s^-1；各重现期波浪要素下海床内部泥沙再悬浮通量的最大值均出现在7⁸m水深处。本文创新点主要有以下三方面：（1）揭示了不同时代沉积形成的现代黄河三角洲沉积物对波浪动力响应过程的差异性，及波浪与海流对沉积物成分、结构、物理力学性质、再悬浮特性的改造作用。（2）建立了波浪作用下沉积物孔隙水压力累积模型，及沉积物超静孔隙水压力累积程度与再悬浮指标间的定量关系。（3）创造性地提出了沉积物波致液化对黄河三角洲沉积物侵蚀再悬浮的控制作用，定量描述了海床内部沉积物向上输运对再悬浮的贡献。更多还原

【Abstract】 The resuspension of sediment by marine hydrodynamics in the modern YellowRiver delta plays an important role in the long-distance transportation and destinationunderstanding of the Yellow River-derived sediments into sea. Existing research onsediment resuspension process and its driving mechanism only focuses on interactionof the wave-current bottom boundary layer, but ignores the role of wave-inducedseabed sediment dynamic response, which is necessary for further research on themodern sedimentary dynamic process. Jointly supported by the National NaturalScience Foundation of China "Storm control on seabed erosion and liquefaction in thesubaqueous Yellow River delta"（Contract No.41072215; Awarded:2011²013） and"Investigation of sources and governing factors of seabed erosion and resuspension inYellow River estuary"（Contract No.41272316; Awarded:2013²016）, thisdissertation reveals the controlling role of seabed dynamic response in sedimentresuspension under waves.Dynamic triaxial experiments and wave flume experiments in laboratory, andwave loading experiments in field are conducted to study sediment dynamic responseto waves in Yellow River Delta. In-situ observations in field and wave flumeexperiments in laboratory are carried out to study sediment resuspension in marinehydrodynamic conditions. Field survey and pit tests are proceeded to study spatial andtemporal distribution characteristic of sediment erodibility of the Yellow River Delta.Dynamic triaxial-scouring flume simulating experiments in laboratory, wave loading-recirculating flume experiments in field, and mathematics statistic analysis andtheoretical calculation are explored to study the control mechanism of waves insediment resuspension. Main findings are demonstrated as follows:（1） Under extreme sea conditions of50-year return period, for various sedimentary areas of the modern Yellow River delta, different levels of pore pressureaccumulation occur in the sediment within4m depth below the seabed surface; forareas in old sedimentation age, the accumulated pore pressure can almost be up to theoverlying sediment effective stress and is characterized by two phases, i.e. slowgrowth and rapid growth; whereas for the other areas, the accumulated pore pressureis less than50%of the overlying effective stress, and the accumulation develops bythree phases, i.e. rapid growth, slow growth and almost flat phase. The pore waterpressure generally presents development patterns of cumulative rise-drasticfluctuation-slow dissipation within30cm depth inside the seabed under heavy waveaction; fine particles inside the seabed are transported upward due to the pore waterpressure accumulation and hence the seabed is coarsened; the older sedimentary ageand the worse size gradation of the undisturbed tidal flat sediment, the strongercoarsening effect.（2） Small-scale sediment resuspension occurs when the nearshore waves arerelatively bigger but the pore water pressure accumulation degree is little, andwave-induced shear stress is the significant driving force; large-scale sedimentresuspension only occurs with high-level pore water pressure accumulation underrough sea condition, when the sediment liquefaction due to waves dominates itsgeneration process. Fine particles inside the seabed that under wave actions aretransported upward and resuspended into water can contribute to a maximum of50%of the total suspended matters.（3） Multi-spatial-temporal scale variations exist in the resuspensioncharacteristics of tidal flat sediments in the modern Yellow River delta. Comparedwith high and middle tidal flat, the sediment in low tidal flat is more prone toresuspension and has higher spatial distribution ununiformity. The resuspension oftidal flat sediments can more easily occur in the north and south part but less in theeast and northeast part of the modern Yellow River delta. The freshly depositedsediments show the similar resuspension characteristics to the undisturbed tidal flatsediments in3to4days due to marine hydrodynamic effects. Sediment resuspensioncharacteristics of the modern Yellow River delta are speculated to rise and fall undergo an evolutionary trend of first increasing and then decreasing over centuries ofsedimentary history.（4） Large-amplitude wave loads can cause linear attenuation of sediment criticalshear stress and threshold velocity, which is closely related to the sediment structuralstrength loss under waves. Sediment critical shear stress and threshold velocity isreduced during the early period of relatively small waves, and stable in smallfluctuations thereafter; the softening of seabed sediments due to pore pressureaccumulation is an important factor in the significant reduction of sediment erodibility,and the later change is accounted for the variation of sediment particles under waves.An estimated formula for seabed internal sediment resuspension flux driven by theaccumulated pore water pressure is established based on the field observations andlaboratory experiments data. The internal sediment resuspension flux is about17⁹1g·m^-2·s^-1under waves in different return periods （5to50years） in Chengdao sea area;the maximum values of internal sediment resuspension flux under waves of differentreturn periods appear in the water at depths of7⁸m.Innovation of this research is composed of the following three aspects:（1） Revealing the diversity of sediment dynamic response to waves for YellowRiver Delta sediments deposited in different ages, and the rework of waves and flowsto sediment composition, structure, physical and mechanical properties, and sedimenterodibility.（2） Constructing the model of pore water pressure accumulation, and therelationship between the degree of excess pore water pressure accumulation and theparameters of sediment resuspension.（3） Creatively putting forward the controlling role of wave-induced sedimentliquefaction in seabed sediment resuspension in the Yellow River Delta, andquantitively describing the contribution of seabed internal sediment upward transportto sediment resuspension.更多还原