Revised Clear-Water and Live-Bed Contraction Scour Analysis (2021) / Chapter Skim
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Pages 39-48
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From page 39... ...
3-1 Laboratory Testing Setup and Test Plan 3.1 Overview As summarized in Chapter 2, the laboratory and numerical applications focused on priority aspects of contraction scour presently not adequately understood or formulated. The laboratory tests were designed to eliminate the deficiencies of earlier investigations that were discovered during NCHRP Project 24-34 (see Section 2.2.2)
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3-2 Revised Clear-Water and Live-Bed Contraction Scour Analysis Figure 3-1. Plan view of the test layout in CSU's 8-ft-wide, 4-ft-deep, 200-ft-long tilting flume.
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Laboratory Testing Setup and Test Plan 3-3 at a Mild contraction ratio of 75% for both clear-water and live-bed conditions. Rigid-bed (non-erodible)
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3-4 Revised Clear-Water and Live-Bed Contraction Scour Analysis and velocity distributions. Data files include tabular and graphical information, as appropriate, and the following: • Metadata associated with each test (e.g., test number, date, discharge, contraction geometry, etc.)
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Laboratory Testing Setup and Test Plan 3-5 4 8 14 25 35 45 60 80 120 200 0 10 20 30 40 50 60 70 80 90 100 0.010.1110 Pe rc en t F in er b y w ei gh t % Grain Size in millimeters GRAIN SIZE DISTRIBUTION Target gradation CSU delivery - Sample 1 CSU delivery - Sample 2 Sieve Size GRAVEL Fine SAND Coarse Medium Fine SILT or CLAY Figure 3-4. Sediment particle size distribution for the CSU contraction scour tests.
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3-6 Revised Clear-Water and Live-Bed Contraction Scour Analysis Test Number Approach width B1 (ft) Contracted width B2 (ft)
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Laboratory Testing Setup and Test Plan 3-7 Figure 3-6 illustrates the flow regions associated with short- and long-contraction effects in a rigid-boundary system. In this figure, region "a" is uniform flow (UF)
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3-8 Revised Clear-Water and Live-Bed Contraction Scour Analysis where hi observed are the observed water surface elevations at the 13 measurement stations, and hi predicted are the water surface elevations at the same stations, as predicted by HEC-RAS for a particular Manning's n. With the optimal n-value for plywood determined from the rigid-bed tests, the same approach was then used to determine the optimal n-value for the observed final conditions with a sand bed, including the ripple-dune bedforms.
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From page 47... ...
Laboratory Testing Setup and Test Plan 3-9 been estimated properly without the results of the rigid-bed (plywood) tests.
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