Mapping Emplaced Articulated Concrete Mattress Using Geoelectrical and Electromagnetic Techniques.

Abstract : Articulated concrete mattresses (ACM) are structures placed parallel to the river current for the purpose of stabilizing the concave banks in river bends, reduce the effects of erosion, and maintain the river channel. Over time, ACM's suffer structural fatigue or become damaged and must be remediated or replaced. The results of this research program reported herein describe the development of rapid, safe, and cost-effective geophysical procedures for detecting, delineating, and assessing the condition of emplaced ACM along the Lower Mississippi River. From 10 geophysical methods evaluated, the self-potential (SP), towed electrical (TDC) resistivity, and electromagnetic (EM) methods were selected for further development This report documents the geophysical concepts, field testing procedures, data analysis methods, results of investigation, and summary of the effectiveness in meeting the research objectives. The ACM is an excellent electrical tar for each geophysical method. Each method implemented can be used in both a high-resolution or reconnaissance mode are able to rapidly detect the presence of ACM and delineate the mattress edges. Depth information to in-service ACM, even when the mat is buried under sediment, is best provided by the TDC resistivity, transient EM, and SP methods. The EM techniques are better in providing condition assessment information and detecting the individual mat segments.