Evaluating the Non-Erodible Cement-Bentonite Barrier Material Samples via Hole Erosion Test Apparatus

Because of the damage that dams, levees, and other water-retaining structures cause, their failure has long been a source of concern. Despite the limitations of the testing apparatus (e.g., HET) used to study barrier material erodibility, they are still widely used. In previous studies, there was very little discussion of the hydraulic parameters (e.g., fluid pressure, flow rate, etc.) obtained from the HET test, particularly how they relate to the varying eroded hole. Therefore, the purpose of this paper was to look into that aspect of the relationship as well as the practical aspects of the HET apparatus that must be considered. Fluctuations in pressure and flow rate data collected during testing were the primary issue discovered. The noise from the pump machinery caused the data collected to fluctuate within a specific range, but the fluctuations were controlled and consistent. Throughout the test, the pressure recorded fluctuated ± 10 kPa below the target pressure, while the flow rate fluctuated approximately 0.3 L/min. The test was performed on a smooth-surfaced, uniform-diameter hole; however, this is not always the case for holes in eroded samples. The non-uniform surface can affect the friction between the eroded surface and the eroding fluid, which in turn affects the pressure loss across the erosion pipe. A non-invasive measurement method for determining the diameter of an eroded hole is suggested for future research, and this study provided an empirical relationship between pressure difference, flow rate, and eroded hole diameter. Despite the limitations, the results provided an overview of the expected fluctuation range from the apparatus as well as the relationship between hydraulic parameters.