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

上平面床/板流输运条件下沉积的内部结构：实验室实验和数值模拟南卡罗来纳大学EAR-1250641的Enrica Viparelli，风暴和浊流侵位的岩石沉积的特征是，在块状单元下面有一个下侵蚀边界，然后是平行的层状单元和交叉的层状单元。这类矿藏被解释为能量流减弱而就位。块状单元在宏观上是无结构的，即沉积物中没有可见的沉积物颗粒组织。在层状单元中，不同大小的泥沙颗粒以可见的模式沉积，本研究的主要目的是调查和模拟导致块状和平行层状单元侵位的水流和泥沙输移条件。实验室和现场研究表明，平行叠层单元是在被称为上平面床型的泥沙输送条件下布置的。这些条件的特征是：1)一到两个颗粒直径厚的移动的推移质层，以及2)向下游迁移的低幅度台地。由于平行叠层单元是在上平面床层状态下沉积的，所以底部单元必须在更密集的输送条件下就位。研究的中心假设是：1)强烈的输运条件对应于席状流，这是一种推移质输运方式，其特征是推移质层直径10-100s厚；ii)席状流可以抑制平行纹层的形成；iii)这种抑制导致连续沉积条件下侵位沉积物颗粒组构趋于均一。必须承认，板状流并不是产生大量沉积物的唯一机制，但它的运行条件通常可以在野外规模上满足。基于初步的实验室实验结果，提出了一个实验和数值程序来表征块状和平行层状沉积物的沉积。在上游平面河床和板流输运条件下，进行明渠，即河床状淤积的室内试验。该实验装置的选择取决于在实验室规模的片状流态中诱导泥沙沉积的需要。然而，这些实验将专门设计来模拟强烈的和净沉积的水下流动。数值程序的中心是开发一个模型，该模型能够再现在上平面床层和板状流输送条件下沉积的颗粒组构。该模型将与实验结果进行对比验证。实验室和数值计算的结果将为以下方面提供必要的信息：1)总体上描述上平面床面和片状水流运动的力学特性；2)将沉积物的颗粒组构与水流和泥沙运动特性联系起来。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的影响。一名研究生将带头进行实验和数值工作，以继续他的博士研究。他还将负责组织实验室和数字数据，并通过CDMS和NCED储存库及时传播这些数据。四名本科生将在三年内被聘用，通过直接由PI监督的本科生研究项目为他们的研究生学习做准备。

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.