Erosion Control of Scour during Construction. Report 4. Stability of Underlayer Material Placed in Advance of Construction to Prevent Scour; Hydraulic Model Investigation.
Technical rept. 1 Oct 81-30 Sep 82,
ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS HYDRAULICS LAB
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When major rubble-mound stone structures are constructed in the coastal zone, they alter the existing current and wave conditions that normally exist at a particular location. Waves breaking on such structures under construction may cause bottom material to be suspended and transported from the region, resulting in scour holes that must be filled with construction material. To minimize potential cost increases due to scour during nearshore construction, a foundation blanket of underlayer material can be placed some distance ahead of the construction of the upper portions of the structure. The stability of such an underlayer material section will depend on the size of the material used in the layer, the extent of the section, and the incoming wave climate. This study sought to determine the stability during construction of such an underlayer material section, which also serves as the foundation blanket for rubble-mound structures constructed on a movable bottom. A simple beach profile consisting of straight, uniform contours parallel with the shoreline was physically modeled on a IV-on-25H slope in a 6-ft-wide wave flume. A major stone structure was assumed to be under construction perpendicular to the shoreline and thus perpendicular to the uniform parallel contours. A two-dimensional section of this stone structure was modeled 16-to-1 linear scale ratio along the major axis of the structure. The waves which produced the most severe movement of the underlayer section scour were those with characteristics that caused breaking with plunging to occur directly at the toe of the rubble-mound structure.
- Physical and Dynamic Oceanography
- Civil Engineering
- Structural Engineering and Building Technology