Time-lapse monitoring of internal erosion in earthen dams and levees using ambient seismic noise

Earthen dams and levees are prone to progressive failure through internal erosion of their structure. Internal erosion is often invisible to current methods of inspection until it manifests itself at the exterior surface. This study focuses on the novel use of passive seismic interferometry to monitor temporal changes in earthen embankments caused by internal erosion. This technique uses the ambient seismic noise – i.e. ambient vibrations – propagating through the structure. Laboratory-scale and field-scale embankment failure experiments are monitored. Seismic impulse responses are reconstructed from the ambient noise and temporal variations in seismic wave velocities are observed throughout each test. The application of seismic interferometry on a canal embankment tested to failure by internal erosion revealed up to 20% reductions in surface wave velocity as internal erosion progressed. The monitoring of a field embankment loaded to partial failure revealed a 30% reduction in averaged surface wave velocity. Some local velocity variations showed good agreement with local pore water pressure responses.