ABSTRACT

Scour is a natural phenomenon involving the removal of bed sediments by the perturbation of flow field with the erection of hydraulic structures such as guide bank, abutments and bridge piers. Removal of sediment at the base of the pier due to scouring not only undermines its foundation support considerably but also leads to deposition and siltation downstream due to lower flow velocities. This deforms the river bed configuration and thereby flow kinematics. While there have been numerous studies of scouring in gravel and sand beds, there are few studies involving fine sand to silt beds. In the present flume-based study, an attempt was made to study the effect of pier size, shape and flow velocity on scouring process, scour depth for piers in fine sand to silt bed. Results reveal that scouring process significantly differs for different pier shapes and sizes. Equilibrium scour depth and downstream bed deformations show considerable correlation with turbulent flow characteristics. Empirical equations have been proposed to predict the maximum equilibrium scour depth. Outcomes of the investigation support and assist engineering practices related to site-specific, cost-effective designs of bridge pier foundations and the consequence on streambed modifications at the lower reach of rivers.

摘要

冲刷是一种自然现象，涉及通过建造导流堤、桥台和桥墩等水工结构，通过扰动流场来去除河床沉积物。由于冲刷清除了码头底部的沉积物，不仅大大破坏了其基础支撑，而且由于较低的流速导致下游沉积和淤积。这会使河床结构变形，从而使流动运动学变形。虽然已经有大量关于砾石和沙床冲刷的研究，但很少有研究涉及细砂到粉砂床。在目前的基于水槽的研究中，试图研究桥墩尺寸、形状和流速对冲刷过程、冲刷深度的影响。结果表明，对于不同的桥墩形状和尺寸，冲刷过程存在显着差异。平衡冲刷深度和下游河床变形与湍流特性显示出相当大的相关性。已经提出了经验方程来预测最大平衡冲刷深度。调查结果支持和协助与特定地点、具有成本效益的桥墩基础设计相关的工程实践，以及对河流下游河床改造的影响。