Reclamation Information Sharing Environment (RISE)

The research discussed in this report investigated whether unique limit state conditions exist if internal erosion due to internal instability is allowed to continue to equilibrium, and the applicability of a rigid wall permeameter test to determine these limit state conditions. The research was conducted at the Geotechnical Laboratory and Field Support (GLFS) group of the Bureau of Reclamation’ Technical Service Center (TSC) in Denver, CO by modifying existing equipment and controlling software. Four tests were conducted on a gap graded internally unstable soil. It was determined that internal erosion, if allowed to continue unimpeded, equilibrates to an end state condition resulting in the equilibration of hydraulic conductivity, height (or volume) change, and stress conditions throughout the specimen in a rigid wall permeameter. Further research is needed to better define end state conditions for soils representing dams in Reclamation’s portfolio. The rigid cell permeameter is applicable for determining equilibrium states for hydraulic conductivity and final gradation. A flexible wall permeameter is required to determine the final volume change and mass loss at the end state of internal erosion and the effect of stress conditions on the end state parameters.