A Geophysical Method of Evaluating Existing Earth Embankments

Abstract

It has long been recognized that earth embankments need periodic inspection and monitoring, especially if settlement or damage is suspected. Currently, earth embankment condition is evaluated through visual inspection and analysis of data from instrumentation such as piezometers and inclinometers. A program to evaluate the condition of existing earth embankments using geophysical methods was developed. This technique is currently being used as part of a safety evaluation of existing earth embankments in the western United States. The geophysical method utilizes the “common offset” seismic refraction technique which emphasizes areas of change. Seismic lines are run along the dam axis and toe. Anomalous areas, if any, are targeted for drilling. Examples of this technique, applied to various dams, are illustrated and the results presented. It is anticipated that a base line data file will be established for all the major earth dams in the United States. New seismic lines could then be run after a dam has undergone an event such as an earthquake and the two sets of data compared. It is also anticipated that more detailed information will be gained from the seismic data as the program continues and drilling data become available for direct comparison.