Centrifuge Modeling Study of Backward Erosion Piping with Variable Exit Size

Abstract

This study presents the results from a series of centrifuge modeling tests conducted to investigate the backward erosion piping across a sandy foundation underlying an impervious cohesive layer with a defined exit hole. Different levels of centrifuge gravitational acceleration and various exit hole sizes were tested. The behavior at different phases of erosion was analyzed based on in-flight video recordings and posttest observations, along with local and global pressure loss measurements. Results showed that the overall mechanism that was modeled was similar to the mechanism described in previous small-scale experimental studies. The results showed that the exit hole size had minimal impact on the critical hydraulic gradient but affected the characteristics of the piping path and the amount of eroded material. The critical hydraulic gradient that initiated the erosion decreased slightly as the centrifuge gravitational acceleration increased. The values of the critical hydraulic gradient, which was studied locally and globally, ranged between 0.15 and 0.40, and fell within a range of estimates from typical analytical methods. This study provides a means to improve the testing protocol and analysis of centrifuge modeling of internal erosion mechanisms, which currently is limited in the literature.