Time-Lapse Monitoring of the Slope Failure Process of a Model Levee

A half-shaped model levee 3 m high and 20 m long with a 3.5-m wide crest was time-lapse monitored over a period of four days. The purpose of the monitoring was to clarify the behavior of water migration in the levee during the deformation process. The time-lapse data included the height of the water table in the levee body measured using a water gauge array, apparent resistivity along a line set on the slope shoulder, surface temperature, and slope surface topography scanned by means of a 3D laser imaging system. Data were acquired basically at 1-hour intervals. Groundwater conditions in the levee body were controlled by infiltration from a perforated tank set at the rear side and supplemental surface watering. Surface deformation was recognized 5 hours after the surface watering, and it took another 2 hours until small slope failure occurred. Resistivity data strongly indicated that infiltration of surface water through the vadose zone and its connection with the water table in the body triggered the surface slope failure.