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Overview

 

Research and Development (R&D) Project Sites

Project Information
Project ID:   FHWA-PROJ-07-0027
Project Name:   Scour Evaluation Studies: Scour in Cohesive Soils and Ex Situ Scour Testing Device
Project Status:   Active
Start Date:  October 1, 2007
End Date:  July 30, 2014
Contact Information
Last Name:  Kerenyi
First Name:  Kornel
Telephone:  202-493-3142
E-mail:  kornel.kerenyi@dot.gov
Office:   Office of Infrastructure Research and Development
Team:   Hazard Mitigation Team [HRDI-50]
Program:   IRT (Infrastructure Research and Technology)
Laboratory:   J. Sterling Jones Hydraulics Laboratory
Project detail
Roadmap/Focus area(s):   Infrastructure Research and Technology Strategic Plan and Roadmap
Project Description:   Scour in cohesive soils is a complicated phenomenon that is far from understood. Conventional approaches to cohesive soil scour prediction are applying laboratory experimental results of cohesionless soils to cohesive soils and are usually overly conservative. Previous research focused on the critical shear stress while the effects of vertical pressure fluctuations on scour initiation were not considered. The fact is that although shear stress moves sediments into motion in sliding or rolling modes, the saltation mode of bedload results from the vertical pressure fluctuations or lift. The objective of this study is to understand the soil and fluid characteristics in the bed boundary flow structure, and establish an incipient motion criterion for cohesive soil scour.
Goals:   The primary objective of this study is to develop design tools for scour in cohesive soils that will be implemented in Hydraulic Engineering Circular No. 18, "Evaluating Scour at Bridges."
Product Type:   Research report
Test Methodology:   This research study will apply various hydraulic loading conditions to a range of different cohesive soils and measure the soil erosion response. The hydraulic loading will be performed using an ex situ scour testing device (ESTD). The ESTD combines couette flow with a moving belt on the top of a gap, approximately 15 cm (0.59 inch) high, and pipe flow to produce a log law velocity profile in the test section. "Couette flow" refers to the laminar flow of a viscous fluid in the space between two parallel plates, one of which is moving relative to the other. The soil sample in the test section is mounted on a sensor that measures shear stresses and vertical forces simultaneously. The erosion rate is determined through the loss of vertical force on the sample.
Expected Benefits:   This research will develop a new design procedure to estimate bridge pier scour in cohesive soils.
Deliverables: Name: Design guidelines for scour in cohesive soils.
Product Type(s): Research report
Description: The primary objective of this study is to develop design tools for scour in cohesive soils that will be implemented in Hydraulic Engineering Circular No. 18, "Evaluating Scour at Bridges."
FHWA Topics:   Roads and Bridges--Hydraulics
TRT Terms:   Scour
Infrastructure
Soils
Research
Bridges
Erosion
Hydraulics
FHWA Disciplines:   Hydraulics
Subject Areas:   Hydraulics and Hydrology

 

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