S-wave Velocity Monitoring During an Artificial Rainfall Experiment Using Large Scale Rainfall Simulator

We conduct the rainfall experiment using a large scale rainfall simulator and an artificial embankment consists of sand and silt in order to evaluate S-wave velocity monitoring for a prediction of a slope failure. The intensity of the rainfall is controlled to maintain 15 to 200 mm/hour for a certain time frame. S-wave velocity cross sections are acquired by MASW survey before, during, and after the controlled rainfall. The obtained cross sections show little change in the S-wave velocity and that is considered to reflect water filtration process in subsurface. The difference is not so significant, but it is confirmed by both waveforms and the dispersion curves calculated from common shot gathers at a fixed shot point. The dispersion curves are included various higher modes and that makes it difficult to evaluate the result; however, the complex higher mode would be useful to derive more information in the future. Compared to the resistivity monitoring, the S-wave velocity monitoring is not so sensitive to the water content; instead, it is relatively easy to be obtained by surface wave method. Therefore, it will be an effective monitoring tool to assess vulnerability of slopes and mitigate damage by natural disasters.