A numerical study into factors affecting stress and pore pressure in free draining mine stopes

This paper presents a modified version of Gibson’s chart that may be used to identify “free draining” mine backfill situations. I.e. fill situations in which the phreatic surface falls below the fill height during filling operations (assuming adequate barricade drainage). A fully coupled multi-physics finite element model is then used to demonstrate the importance of computing the elevation of the phreatic surface as part of the simulation, rather than specifying it as done in many previous models. A parametric study is presented to identify material properties that most significantly influence the pore pressures and barricade stresses within a free draining mine stope. It is shown that the soil–water retention properties influence pore pressures most significantly, while barricade stress is influenced by the strength (particularly the cemented component), the coefficient of at rest earth pressure as well as soil–water retention properties.