The quantification of the erodibility of cohesive sediments is fundamental for an advanced understanding of estuarine sediment transport processes. In this study, the surface erosion threshold τc for cohesive sediments collected from two sites in the area of the Port of Hamburg in the River Elbe is investigated in laboratory experiments. An improved closed microcosm system (C-GEMS) is used for the erosion experiments, which allows the accumulation of suspended sediment concentration (SSC) over an experimental run. A total of 34 erosion experiments has been conducted with homogenized samples and bulk densities between 1050 kg/m³ and 1250 kg/m³. The covered range of bulk densities is seen to represent the values commonly exhibited by freshly deposited cohesive sediments. Two approaches to derive τc based on the erosion rate (ε-method) and the SSC (SSC-method) were elaborated and compared. For both approaches, only one parameter has to be set in order to facilitate transferability to other devices. The results show a better performance of the SSC-method in terms of lower uncertainties, especially at the upper application limits of the utilized C-GEMS. The application of the SSC method yields values for τc between 0.037 N/m² and 0.305 N/m², continuously increasing with bulk density. Repetition tests proved the repeatability of the experimental procedure and utilized methods to derive τc. The derived data for τc is used to fit two mathematical models: i) a highly empirical model relating τc to dry bulk density and ii) a recently proposed model relating τc to the physical properties of the sediment-mixture. While the derived parameters for the first model vary widely for the two sampling sites, the fit-parameter for the latter model is virtually independent of the investigated site, suggesting the superiority of this approach.

中文翻译：

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使用封闭的微观系统导出汉堡港新沉积的粘性沉积物的侵蚀阈值

粘性沉积物侵蚀性的量化对于深入了解河口沉积物输送过程至关重要。在本研究中，表面侵蚀阈值τC在实验室实验中对从易北河汉堡港地区的两个地点收集的粘性沉积物进行了研究。改进的封闭微观系统（C-GEMS）用于侵蚀实验，允许在实验运行中积累悬浮沉积物浓度（SSC）。总共进行了 34 次侵蚀实验，样品均质且堆积密度在 1050 kg/m3 至 1250 kg/m3 之间。所覆盖的堆积密度范围被认为代表了新沉积的粘性沉积物通常表现出的值。两种推导方法τC基于侵蚀率（ε-方法）和SSC（SSC-方法）进行了阐述和比较。对于这两种方法，只需设置一个参数即可方便转移到其他设备。结果表明，SSC 方法在不确定性较低方面具有更好的性能，特别是在所用 C-GEMS 的应用上限方面。 SSC 方法的应用产生了以下值：τC0.037 N/m² 至 0.305 N/m² 之间，随堆积密度不断增加。重复测试证明了实验过程的重复性，并利用方法推导τC。得出的数据为τC用于拟合两个数学模型：i）与τC干容重和 ii) 最近提出的一个相关模型τC沉积物混合物的物理性质。虽然第一个模型的推导参数对于两个采样点差异很大，但后一个模型的拟合参数实际上独立于调查地点，这表明该方法的优越性。