Preliminary Implementation of Geophysical Techniques to Monitor Embankment Dam Filter Cracking at the Laboratory Scale

Internal erosion presents a significant hazard to water retaining structures and is most often identified in its progressive stages through visual inspections or observations. Acoustic or ultrasonic methods in combination with electrical geophysical methods can be used as a tool for detection and continuous monitoring of subsurface internal erosion initiation in its early stages. This research investigates passive acoustic emission, self potential, and cross-hole tomography for suitability as long-term, remote and continuous monitoring techniques for internal erosion and cracking of embankment dams. Geophysical data from the three techniques have been collected during manually imposed cracking of granular filter materials. Specifically, data has been collected during both self-healing (i.e., desirable filter behavior) and during continuing erosion (i.e., undesirable filter behavior). The data is compared to baseline, pre-crack data. This proof-of-concept research provides evidence of these geophysical techniques for effective monitoring of embankment cracking as a precursor to internal erosion. This paper presents the details of the instrumentation systems, data acquisition parameters, and early findings from the research. 2D seismic velocity tomograms, passive acoustic and passive electrical signatures associated with cracking and suffusion are discussed. .