The internal structure of deposits emplaced under upper plane bed / sheet flow transport conditions: Laboratory experiments and numerical modeling

上层平面床/席状流输运条件下沉积物的内部结构：实验室实验和数值模拟

• 批准号: 1250641
• 负责人: Enrica Viparelli
• 金额: $ 20.17万
• 依托单位: University of South Carolina at Columbia
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-04-01 至 2017-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1250641&HistoricalAwards=false
• 关键词: internal; structure; deposits; emplaced; under

The internal structure of deposits emplaced under upper plane bed/sheet flow transport conditions: Laboratory experiments and numerical modelingEnrica Viparelli, EAR-1250641, University of South CarolinaABSTRACTRock deposits emplaced by storms and turbidity currents can be characterized by a lower erosional boundary underlying a massive unit followed in ascending order by a parallel laminated unit and a cross laminated unit. Such deposits are interpreted to be emplaced by waning energy flows. Massive units are macroscopically structureless, i.e. there is not a visible organization of sediment particles within the deposit. In the laminated units, sediment particles of different size are deposited with visible patterns.The main objective of this research is to investigate and model flow and sediment transport conditions that are responsible for the emplacement of massive and parallel laminated units. Laboratory and field studies demonstrate that parallel laminated units are emplaced under sediment transport conditions known as upper plane bed regime. These conditions are characterized by i) a moving bedload layer one or two grain diameters thick, and ii) downstream migrating low amplitude bedforms. As the parallel laminated unit is deposited under upper plane bed regime, the basal unit has to be emplaced under more intense transport conditions. The central hypotheses of the proposed research are that i) those intense transport conditions correspond to sheet flow, which is a mode of bedload transport characterized by a bedload layer 10-100s grain diameters thick, ii) the sheet flow layer can suppress the formation of parallel laminations, and iii) this suppression results in a tendency to homogenize the grain fabric of the emplaced deposit under conditions of continued deposition. It must be acknowledged that sheet flow is not the only mechanism that produces massive deposits, but the conditions for it to operate can be commonly met at field scale.Based on the results of preliminary laboratory experiments, an experimental and numerical program is proposed to characterize the deposition of massive versus parallel laminated deposits. Open channel, i.e. river-like, laboratory experiments will be performed to build a deposit under upper regime plane bed and sheet flow transport conditions. The choice of this experimental setting is dictated by the need to induce sediment deposition in the sheet flow regime at laboratory scale. However, the experiments will be specifically designed to model intense and net-depositional subaqueous flows. The numerical program is centered on the development of a model that is able to reproduce the grain fabric of the deposits emplaced under upper plane bed and sheet flow transport conditions. The model will be validated against the experimental results. The results of the laboratory and numerical work will provide the necessary information to i) characterize the mechanics of upper plane bed and sheet flow transport regimes in general, and ii) relate the grain fabric of the deposit to the characteristics of the flow and the sediment transport. They are thus expected to have a transformative impact on the communities studying subaqueous sedimentary processes, coastal and deep-water engineering. One graduate student will take the lead in the performance of the experimental and numerical work to pursue his PhD research. He will also be responsible for the organization of the laboratory and numerical data and for their timely dissemination through the CDSMS and the NCED repositories. Four undergraduate students will be hired in three years to prepare them for graduate studies via undergraduate research projects that will be directly supervised by the PI.

沉积物的内部结构侵位在上平面床/席流运输条件下：实验室实验和数值模拟Enrica Viparelli，CN-1250641，南卡罗来纳大学摘要风暴和浊流侵位的岩石沉积物可以通过下侵蚀边界下的一个大规模的单位，其次是一个平行的层压单位和交叉层压单位上升的顺序。 这些矿床被解释为是由能量流减弱而形成的。 块状单元在宏观上是无结构的，即在存款内没有沉积物颗粒的可见组织。 在层状单元中，不同尺寸的沉积物颗粒沉积有可见的图案。本研究的主要目的是调查和模拟的流动和泥沙输运条件，负责大规模和平行的层状单元的就位。 实验室和野外研究表明，平行层状单元是在沉积物搬运条件下（称为上平面床态）沉积的。 这些条件的特点是：i）一个移动的推移质层，一个或两个粒径厚，和ii）下游迁移低振幅的底形。 由于平行叠层单元是在上平面床状态下沉积的，因此基底单元必须在更强的输运条件下就位。 本研究的中心假设是：i）这些强烈的输运条件对应于片流，片流是一种以10- 100 μ m粒径厚的推移质层为特征的推移质输运模式，ii）片流层可以抑制平行层纹的形成，和iii）这种抑制导致在连续沉积的条件下使所安置的存款的颗粒组构均匀化的趋势。 必须承认，片流是不是唯一的机制，产生大量的存款，但它的操作条件，可以在现场scale.Based上的初步实验室实验结果，提出了一个实验和数值程序来表征沉积的大量与平行层状存款。 将进行明渠（即类似河流）的实验室试验，以在上部流态平床和薄层流输运条件下建立存款。 这个实验设置的选择是由需要在实验室规模的片流制度诱导沉积物沉积。 然而，实验将专门设计用于模拟强烈和净沉积的水下流动。 数值程序的中心是一个模型，能够再现的沉积物的颗粒织物的发展上平面床和片流运输条件下。 该模型将根据实验结果进行验证。 实验室和数值计算工作的结果将提供必要的信息，i）表征上平面河床和薄层水流输运状态的力学特性，ii）将存款的颗粒结构与水流和泥沙输运特性联系起来。 因此，预计它们将对研究水下沉积过程、沿海和深水工程的社区产生变革性影响。一名研究生将带头进行实验和数值工作，以进行他的博士研究。 他还将负责组织实验室和数值数据，并通过CDSMS和NCED储存库及时传播这些数据。 四名本科生将在三年内被雇用，通过将由PI直接监督的本科研究项目为他们的研究生学习做准备。