OHIO RIVER LEVEE SEEPAGE AND STABILITY EVALUATION USING GEOPHYSICAL CHARACTERIZATION

摘要

Many of the nation's levees were built more than 50 years ago with the intent of protecting crops from flooding. Over the last several decades, as housing and commercial development on land protected by levees has taken place, the risk to public health and safety and property damage associated with potential levee failure has also dramatically risen. This is notable along many segments of the Ohio River, where the levee systems constructed since the 1940s by the U.S. Army Corps of Engineers (USACE) have long since exceeded their design lives. In addition, changes to the Rivers hydrologic dynamics have also occurred due to both development and the construction of dams. This paper will focus on a case study of the evaluation of one large, combined levee system along the Ohio River and lessons learned from the use of geophysical surveys to support the assessment of seepage potential and levee.stability. With more than five lineal miles (26,800 feet) of levee embankment and foundation soils to evaluate, the use of geophysical surveys supplemented previous widely-spaced boring information to confirm the thickness and quality of an upper clay blanket layer and the underlying pervious foundation aquifer down to bedrock. The geophysical survey techniques included the completion of both electromagnetic (EM terrain conductivity on the levee itself and two-dimensional electrical resistivity imaging (2D-ERI) through the foundation soils. The results were calibrated against previous soil boring and geotechnical engineering testing data to help identify the location of more critical, potentially higher permeability zones for further evaluation and/or analyses by additional direct soil sampling and testing, field hydraulic testing and long-term water level monitoring.