Failure Mechanism of a Granular Bed Induced by a Horizontal Water Jet Using Particle Image Velocimetry

Abstract

Particle image velocimetry (PIV) was used to investigate the failure mechanism of a granular bed subjected to a water jet emerging laterally from a vertical, impermeable face. Experiments were performed in a modified seepage tank made of plexiglass with dimensions of 700 × 600 × 103 mm. The bed of particles was subjected to a lateral seepage flow at a controlled rate, and the motion of the particles was recorded using a digital camera. Measurements of flow and pore pressure were also made. Several stages of failure were observed during the repeated experiments: 1) outwards movement of the particles (horizontally and vertically upwards), 2) cavity formation, 3) cavity enlargement, and 4) the emergence of a fluidised zone at the bed surface. Trends relating to the flow rate of fluid flow to the onset of failure were also noted. The PIV analyses revealed the movement of sand grains and boundaries between regions in which sand grains either did or did not move. An analytical model based on the Ergun equation is presented to predict the onset of failure. This study provides valuable insights into the failure mechanism of granular materials triggered by lateral seepage flow.