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: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=686802
• 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，在某些地区，冰盖最多可以持续六个月。在冰覆盖的条件下，最大流速的位置比开放条件下的河床更靠近河床。因此，在没有冰盖的情况下，冰盖下桥墩周围的河床冲刷深度要大。过度的冲刷可能会损害桥梁码头的基础，例如，1966年，史密瑟斯（Smithers）的16号高速公路桥的倒塌发生，并于2018年在布鲁斯港（Port Bruce）发生桥梁倒塌。拟议的研究将帮助我们更好地了解具有不同维度，冰层和安排不同尺寸的码头周围的地方冲刷过程。这项研究将为土木工程师提供可靠的结果，可用于修改桥梁设计指南，以考虑冰盖的影响。冲浪过程对流量的依赖性*强度，颗粒大小，覆盖条件，多个墩的排列以及*压缩的马在冰盖下的压缩马匹涡流，以及（d）开发一个数值模型，用于模拟冰层下的多个墩周围的局部冲刷过程。将使用五种不同的非均匀沙子。聚苯乙烯泡沫塑料板将用作模拟的冰盖（光滑，粗糙且*非常粗糙）。在开放流和冰覆盖的条件下对实验数据的分析将*集中在非二维变量上，例如剪切雷诺数，盾牌*参数和桥梁码头*尺寸。将建立方程式以确定冰盖下的冲刷深度。 ***建模冲刷过程将包括建模涉及流场，沉积物传输和*床形态的强耦合系统。数值模型将由*三个模块组成：用于模拟多个码头周围流场*的流体动力模块，用于建模悬挂*沉积物传输的沉积物模块，以及一个床变体模块，以说明*床超图的变化。模拟流场周围的流场的优先级之一*是解决基础架构周围的涡流系统。为了求解*涡流系统，将使用不稳定的兰率（雷诺平均的NavierStokes方程）或大型涡流模拟来*解决马蹄形涡流。标准的K- Epsilon湍流模型将*首先在冰盖下的多个桥墩*周围的流场模拟中使用。基于RNG的K-Epsilon湍流模型也将用于*模拟。**