Using Geophysics to Assess the Condition of Small Embankment Dams

Abstract

The U.S. Army Engineer Research and Development Center (ERDC) Geotechnical and Structures Laboratory conducted a program of technical and archival research to document current knowledge of indirect seepage detection and methods for monitoring the conditions within small embankment dams. This report documents current methods used to determine conditions within embankment dams by indirect means and provides guidance on determining which methods will most likely succeed at various sites. The report includes a review of current indirect geophysical technologies used in seepage investigations with emphasis on small-sized earthen dams (<7,500 m long, <40 m high). A summary of state-ofthe-art equipment, principles of operation, and field procedures is also presented, followed by the results of a September 2003 geophysics-based investigation of seepage and conditions within Clearwater Dam in southeastern Missouri. The report concludes with recommendations for future development of the most promising technologies to be used for seepage detection and assessing the condition within embankments.

Geophysical Methods and their Applications in Dam Safety Monitoring

“…Anomalous recordings could also result from numerous sources other than seepage flow, such as electrochemical activity created through oxidation reactions, groundwater recharge, and telluric currents to name few. However, surveys can be conducted with proper consideration for other sources, leading to appropriate interpretation of seepage anomalies from (SP) data [35]. The main advantages of self-potential are: (i) Self-potential survey is conducted mainly for detecting the seepage or leakage from or through engineering structures like dams, dikes, landslide zones, canals weirs etc.…”

“…Ideally, investigations should include more than one method and then the results should be tied into existing borehole data to provide the best seepage characterization results. Geological data from the boreholes give a context to data interpretation by defining what geologic features are possible or likely [22]. Lastly, it may be said that geophysicists and civil engineers should work hand in hand in order to build and maintain dam structures to avoid the damage and waste of resources that may eventually result in the project if done otherwise.…”