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，某些地区的冰盖可持续长达六个月。在冰覆盖条件下，最大流速的位置比在开放流条件下更靠近河床。因此，冰覆盖下桥墩周围的河床冲刷深度大于无冰覆盖时的河床冲刷深度。过度冲刷可能会对桥墩基础造成损坏，例如 1966 年 BC 省史密瑟斯 16 号高速公路桥梁的倒塌和 2018 年安大略省布鲁斯港桥梁倒塌所发生的情况。拟议的研究将帮助我们更好地了解当地的冲刷过程围绕冰盖下具有不同尺寸、形状和布置的多个码头。这项研究将为土木工程师提供可靠的结果，可用于修改考虑冰盖影响的桥梁设计指南。这项研究将解决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）调查多个桥墩的尺寸/形状/排列对冰下局部冲刷过程的影响(c) 建立方程来描述冲刷过程对水流强度、颗粒尺寸、覆盖条件、多个桥墩的布置以及冰盖下的压缩马蹄涡的依赖性，以及 (d) 开发用于模拟的数值模型冰层覆盖下多个码头周围的局部冲刷过程。大量实验将在长80米、宽2米、深1.3米的大型水槽中进行。将使用五种不同的不均匀沙子。聚苯乙烯泡沫塑料片将用作模拟冰盖（光滑、粗糙和非常粗糙）。对开放流和冰覆盖条件下的实验数据的分析将集中于无量纲变量，例如剪切雷诺数、盾牌参数和桥墩尺寸。将建立方程来确定冰盖下的冲刷深度。 冲刷过程建模将包括对涉及流场、沉积物输送和河床形态的强耦合系统进行建模。该数值模型将由三个模块组成：用于模拟多个桥墩周围流场的水动力模块、用于模拟悬浮泥沙输送的沉积物模块以及用于考虑河床地形变化的河床变化模块。本研究还将对多个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首要任务之一是解决基础设施周围的涡系统。为了求解涡系统，将使用非定常 RANS（雷诺平均纳维-斯托克斯方程）或大涡模拟来求解马蹄涡。标准k-epsilon湍流模型将首先用于冰层下多个桥墩周围流场的模拟。基于 RNG 的 k-epsilon 湍流模型也将用于模拟。