Underwater Installation of Filter Systems for Scour and Erosion Countermeasures, Volume 1: Research Report (2018) / Chapter Skim
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Pages 89-102
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3.1 3. LABORATORY TESTING - DOCUMENTATION OF UNDERWATER FILTER INSTALLATION PROCEDURES 3.1 Overview A variety of means and methods are available for placing filter materials underwater, and in flowing water.
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3.2 Granular filters: • Pea gravel mixed equally with 0.6 mm masonry sand and placed with a 2-inch diameter rigid tremie pipe at various elevations above the bed; d50 = 4.0 mm. • Nominal 3/8-inch (9 mm)
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3.3 (a) Construction of lower section of pier within the sediment recess (looking downstream)
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3.4 (a) Flume test at 4-foot depth and 200 ft3/s, approach velocity ≈ 3.5 ft/s.
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3.5 (a) Cross section 12.6 (40 feet upstream of pier)
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3.6 (a) Cross section 12.6 (40 feet upstream of pier)
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3.7 3.3 Underwater Installation of Granular Filters 3.3.1 Critical Velocity vs. Particle Size Placing a granular filter in flowing water requires knowledge of the flow velocity that would be expected at the job site during the construction season.
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3.8 3.3.2 Dispersion and Segregation Issues When placed in flowing water, granular filter materials will disperse and segregate unless placed directly on the bed. Therefore, it is important to utilize uniformly-sized filter gradations and not allow loose dumping from the water surface.
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3.9 Figure 3.9. Grain size distribution curves for dispersion test at 50 ft3/s.
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3.10 Table 3.1. Results of Granular Filter Dispersion Tests.
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3.11 (a) Solids handling pump.
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3.12 (a) Underwater photo of diver placing loose pea gravel around pier at 50 ft3/s flow rate.
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3.13 Figure 3.15. Self-sinking geotextile filter.
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3.14 (a) Unsatisfactory placement of the buoyant geotextile during the 200 ft3/s test run.
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