As part of the Comprehensive Everglades Restoration Project (CERP), the Jacksonville District of the U.S. Army Corps of Engineers is designing an impoundment embankment cross-section. The structure is intended to comprise the perimeter of a water supply basin. The conceptual cross-sections feature interior step and berm embankment faces to armor the containment levee, reduce wave overtopping to acceptable levels, and control reflected wave energy. The goal of the study was to develop engineering guidance for optimizing the structure crosssection to provide the minimum structure that met both wave overtopping and wave pressure design criteria. A small-scale physical model study of waves impacting and overtopping the embankment was conducted. A parallel effort was also completed using the Cornell Breaking Waves and Structure (COBRAS) numerical model based on the Reynolds-averaged Navier Stokes (RANS) equations. The COBRAS model was shown to predict both wave overtopping and hydraulic pressures on the embankment well. An empirical equation was developed to predict wave overtopping as a function of structure configuration and wave and water level conditions. The study concluded that the stepped structure with no berm was optimal at reducing overtopping. The structure with continuous steps inhibits turtle egress from the basin. Therefore, guidance is provided for smooth slopes as well as for slopes employing separated blocks for overtopping reduction. The maximum pressures were shown to vary unpredictably with increasing berm width and depth. The maximum pressure was generally higher for the stepped structure without a berm than for the sections with berms. The highest pressures on the embankment appeared to be more a function of the details of the breaking wave interacting with the structure face than the structure geometry.
Levee breaching is a widespread issue that has had few technological improvements in history. Recent severe flooding situations have created a critical need for a rapid levee repair capability that can function in a wide range of different environments. For levee repair capabilities to make a substantial difference in interior flood levels and damages, they must act very quickly and minimize the chance of additional "unraveling" along the levee. A successful technology must be capable of functioning in extremely austere situations with little conventional logistics support and little or no site preparation. One alternative is to use the one resource readily available during floods; water, as the main structural element in conjunction with high-strength fabrics. The incompressibility of water in a closed high-strength fabric tube can create a stable geometric configuration capable of resisting deformation through a breach. In September 2008 three concepts for levee repair and protection were tested and demonstrated in a 1:4 scale physical model at the Hydraulic Engineering Research Unit, Agricultural Research Service in Stillwater, Oklahoma. Test results will be discussed.
An innovative breakwater system has been introduced for use in areas with thick soft seafloor, utilizing suction piles as the foundations. Gravity-type concrete caissons are placed on top, which resist the lateral loads caused by the wind and waves to protect the harbor behind. In Dec. 2004, four large concrete suction piles were prefabricated and installed successfully in southern Korea. During the installation of suction piles, detailed measurements were made on one pile, including the suction pressure vs. pile penetration relationship. They were used to estimate the mobilized soil strength during the suction pile installation. The calculated mobilized soil strength variation was then expressed as a function of a non-dimensional parameter that included the most essential parameters governing the behavior of suction piles during installation.
As part of the Monitoring Completed Navigation Projects (MCNP) program "Periodic Inspections" work unit, five breakwaters from the Hawaiian Islands were inspected. The Hilo, Kahului east and west, Laupahoehoe, and Nawiliwili breakwaters were examined by walking inspection in the summer of 2005. Broken, cracked, and shifted concrete armor units and stones were recorded, and overall performance of the structure was noted. Photographs were taken and detailed notes recorded at each damage site. Observations and assessments are included for each of the five breakwaters inspected.
The U.S. Army Engineer Research and Development Center (ERDC) solves the nation's toughest engineering and environmental challenges. ERDC develops innovative solutions in civil and military engineering, geospatial sciences, water resources, and environmental sciences for the Army, the Department of Defense, civilian agencies, and our nation's public good. Find out more at www.erdc.usace.army.mil. To search for other technical reports published by ERDC, visit the ERDC online library at http://acwc.sdp.sirsi.net/client/default.
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