Author: Lyndell Z. Hales
Publisher:
Published: 1980
Total Pages: 160
ISBN-13:
DOWNLOAD EBOOK →It is frequently necessary to construct large engineering works of improvement in the surf and nearshore zone to protect harbor entrances, recreational beaches, and navigation channels. Shallow-water surface-gravity waves breaking on the structure during construction will cause bottom material to be suspended and transported from the region by longshore or other currents that may exist. This removal of material is often not compensated by an influx of additional material, and the result is a scour hole, or erosion, which usually develops along the toe of the structure. In order to ensure structural stability and functional adequacy of the works of improvement, any scour area must be filled with nonerosive material (sufficiently stable to withstand the environmental forces to which it will be subjected). This may result in additional quantities of material being required during construction which can potentially lead to substantial cost overruns. The objective of this study is to develop techniques to minimize and control scour during nearshore construction, and to predict the probable magnitude of scour that may result as a function of the wave climate.
Author: Lyndell Z. Hales
Publisher:
Published: 1983
Total Pages: 218
ISBN-13:
DOWNLOAD EBOOK →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.