Evaluating Sand Particle Behavior in Liquefaction through Video Analysis of Ring Shear Experiments with a Transparent Shear Box.

Abstract

This research conducts undrained ring shear tests with a transparent acrylic shear box, and video analysis based on videos of sand particles in the upper shear box taken from the side to evaluate sand particle behavior during liquefaction. In this test, silica sand No. 2 with large grain size (D50=1.98mm) was used to facilitate video analysis. Undrained cyclic loading tests are performed, followed by undrained monotonic loading tests at a constant shear rate by speed control while maintaining undrained conditions and constant normal stress control. After the cyclic shear test and monotonic shear test, drainage and reconsolidation under drained conditions are performed while maintaining constant normal stress. This series is one stage, and three stages of testing are performed on a single specimen. In this study, the behavior of sand particles during loading was captured by a digital video camera, and the horizontal displacement, vertical displacement, and rotation angle of the sand particles were derived. The video analysis revealed differences in the behavior of sand particles when cyclic mobility occurred and when it did not occur. During cyclic mobility, the horizontal displacement and rotation angle vibrate larger near the shear plane, indicating that the particles near the shear plane not only experienced horizontal movement but also rotational motion. On the other hand, the vertical vibrations are nearly uniform regardless of the vertical location. Therefore, uniform vertical vibrations and dilatancy could be induced by the overtaking or rotational motion of particles near the shear plane.