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: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=714752
• 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 NavierStokes 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。 这项研究将解决一些 科学文献中的重要空白，包括：(a) 评估多个桥墩周围的局部冲刷过程 在冰层覆盖下，(b) 调查 多个桥墩的尺寸/形状/布置对局部冲刷的影响 冰盖下的过程，(c) 建立描述冲刷过程对流量依赖性的方程 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，以及（d）开发模拟局部冲刷的数值模型 冰层覆盖下多个码头周围的过程。 广泛的 实验将在80米长的大型水槽中进行， 宽2米，深1.3米。五种不同的不均匀沙子将被 用过的。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进行分析 关注无量纲变量，例如剪切雷诺数、屏蔽数 参数及桥墩 方面。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、泥沙输送和流场的强耦合系统进行建模。 床形态。数值模型将包括 三个模块：水动力模块，用于流场模拟 围绕多个桥墩，一个用于模拟悬浮物的沉积物模块 沉积物输送和床层变化模块来解释沉积物的变化 河床地形。 局部冲刷的数值研究 目前的研究还将围绕多个桥墩进行。一 多桥周围流场模拟的优先顺序 码头是解决周围涡流系统的基础设施。为了解决 涡流系统，非定常 RANS（雷诺平均纳维斯托克斯方程）或大涡模拟将用于 解决马蹄涡。标准 k-epsilon 湍流模型为 首次用于多桥墩周围流场的模拟 在冰盖下。基于 RNG 的 k-epsilon 湍流模型也将用于 模拟。