Riverbed deformation around multiple pile bridge piers under ice-covered conditions - experimental study in a large-scale flume and numerical simulation

冰覆盖条件下多桩桥墩周围河床变形——大型水槽试验研究与数值模拟

• 批准号: RGPIN-2019-04278
• 负责人: Sui, Jueyi
• 金额: $ 2.62万
• 依托单位: University of Northern British Columbia
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=737530
• 关键词: Riverbed; deformation; around; multiple; pile

In Canada, ice cover can last up to six months in some regions. Under ice covered conditions, the location of maximum flow velocity is closer to the riverbed than during open flow conditions. Thus, riverbed scour depth around bridge piers under ice cover is greater than in the absence of ice cover. Excessive scour can cause damage to bridge pier foundations, such as occurred with the collapse of the Highway 16 bridge in Smithers, BC in 1966 and the bridge collapse in Port Bruce, ON in 2018. The proposed research will help us better understand local scour processes around multiple piers with different dimensions, shapes and arrangements under ice cover. This study will provide civil engineers with reliable results that can be used to modify bridge design guidelines that take the impact of ice cover into consideration. This research will address some important gaps in the scientific literature, including, (a) assessing local scour processes around multiple piers under ice cover, (b) investigating the impacts of the dimension/shape/arrangement of multiple piers on local scour processes under ice cover, (c) establishing equations describing the dependence of scour processes on flow intensity, particle size, cover conditions, arrangement of multiple piers, and compressed horse-shoe vortex under ice cover, and (d) developing a numerical model for simulating local scour processes around multiple piers under ice cover. Extensive experiments will be carried out in a large scale flume which is 80-meters long, 2-meters wide and 1.3-meters deep. Five different non-uniform sands will be used. Styrofoam sheets will be used as simulated ice cover (smooth, rough and very rough). Analyses of the experimental data under both open-flow and ice-covered conditions will focus on non-dimensional variables, such as shear Reynolds number, Shields parameter and bridge pier dimensions. Equations will be established to determine the scour depth under ice cover. Modeling the scour process will include modeling a strongly coupled system involving flow field, sediment transport and bed morphology. The numerical model will consist of three modules: a hydrodynamic module for the simulation of the flow field around multiple piers, a sediment module for the modeling of suspended sediment transport, and a bed variation module to account for the change in the bed topography. Numerical studies of the local scour around multiple bridge piers will also be undertaken in the present research. One of the priorities for the simulation of flow fields around multiple bridge piers is to solve the vortex systems around the infrastructure. To solve the vortex systems, either unsteady RANS (Reynolds-averaged Navier-Stokes equations) or Large Eddy Simulation will be used to resolve the horseshoe vortex. The standard k-epsilon turbulence model will be used first in the simulation for the flow field around multiple bridge piers under ice cover. The RNG-based k-epsilon turbulence model will also be used in the simulation.

在加拿大的一些地区，冰盖可以持续长达六个月。在冰覆盖条件下，最大流速的位置比开放条件下更靠近河床。因此，有冰条件下桥墩周围的河床冲刷深度大于无冰条件下。过度冲刷会对桥梁桥墩基础造成损害，比如1966年不列颠哥伦比亚省史密瑟斯16号公路大桥的倒塌，以及2018年安大略省布鲁斯港大桥的倒塌。该研究将有助于我们更好地了解不同尺寸、形状和排列方式的多个冰墩周围的局部冲刷过程。这项研究将为土木工程师提供可靠的结果，可用于修改考虑冰层影响的桥梁设计指南。本研究将填补科学文献中的一些重要空白，包括：(a)评估冰盖下多个桥墩周围的局部冲刷过程，(b)研究多个桥墩的尺寸/形状/布置对冰盖下局部冲刷过程的影响，(c)建立描述冲刷过程对流动强度、粒径、覆盖条件、多个桥墩布置和冰盖下压缩马蹄形涡的依赖关系的方程。(d)建立了一个模拟冰盖下多个桥墩周围局部冲刷过程的数值模型。大量实验将在长80米、宽2米、深1.3米的大型水槽中进行。将使用五种不同的非均匀砂。聚苯乙烯泡沫板将用作模拟冰盖（光滑，粗糙和非常粗糙）。对自由流动和冰雪覆盖条件下的实验数据的分析将重点放在非量程变量上，如剪切雷诺数、盾构参数和桥墩尺寸。将建立方程来确定冰盖下的冲刷深度。对冲刷过程的建模将包括对一个强耦合系统的建模，该系统涉及流场、沉积物输运和河床形态。数值模型将由三个模块组成：水动力模块，用于模拟多个桥墩周围的流场；泥沙模块，用于模拟悬浮泥沙输运；河床变化模块，用于解释河床地形的变化。本研究还将对多桥墩周围的局部冲刷进行数值研究。多桥墩周围流场模拟的重点之一是解决基础设施周围的涡流系统。为了求解马蹄形涡系统，将采用非定常RANS （reynolds -average Navier-Stokes方程组）或大涡模拟来求解马蹄形涡。首先采用标准k-epsilon湍流模型对多桥墩冰覆盖下的流场进行模拟。基于rng的k-epsilon湍流模型也将用于模拟。