Geophysical Monitoring Techniques for Underwater Landslide in 1g Models

Abstract

Underwater landslides along coastal regions can be considerably large and yield many potential hazards. Many laboratory experiments have been carried out by modeling submerged landslides to understand their failure mechanisms and to develop useful design and construction concepts in an attempt to overcome these problems. This paper presents the implementations of three high resolution geophysical techniques including electrical resistance profile, ultrasonic compressional wave reflection imaging, shear wave geotomography, and a pressure-based method to investigate lab-scaled submerged mass movements of layered soil specimens. Electrical resistance profiles of a soil mass obtained by inserting an electrical resistance probe provide the spatial distribution of soil layers. Ultrasonic reflection images based on the acoustic impedance mismatch between materials are applied to detect layers and landslides with sub-millimeter resolution. Pixel-based images of underwater landslides are created by the inversion of the boundary information derived from the travel times of shear waves. The changes of vertical total stress caused by landslides are detected by using flexible stress sensors in the pressure-based method. The experimental results show that the electrical resistance, ultrasonic wave imaging, and total stress change can provide complementary information, and their associations with a shear wave velocity tomography image provide a better understanding of underwater landslides. This study suggests that these geophysical techniques may be effective tools for the investigation of underwater landslides simulated by a shaking table and centrifuge testing.