Three-dimensional method of fragments to study drainage through hydraulic fill stopes

The method of fragments is a simple technique for determining the flow rate, pore water pressure, and exit gradient in two-dimensional confined flow problems. This method is extended to a three-dimensional hydraulic fill stope. Expressions were developed for computing the flow rate and the maximum pore water pressure within the stope, which are two important design parameters for analyzing the drainage characteristics of the stope during filling. These expressions were validated using laboratory tests on model stopes and a numerical model using an explicit finite difference code, and good agreement was observed. The equations developed in this research note enable quick estimates of flow rate and the maximum pore water pressure within the hydraulic fill stope, without resorting to sophisticated simulation models. It is shown that the method of fragments can be applied to three-dimensional seepage problems, provided that appropriate form factors are developed