Numerical Analysis of Stress Distribution in Backfilled Stopes Considering Interfaces between the Backfill and Rock Walls

Mining backfill is widely used in underground mines worldwide. The stresses in backfilled stopes must be correctly evaluated because they influence the ground stability and the required strength of exposed (horizontally or vertically) cemented backfill. The stress estimation can be accomplished by numerical modeling with or without the use of interface elements between the backfill and rock walls. To date, most numerical models have been developed without the use of interface elements, and only a few have used interface elements with the same shear strength as the backfill. Stress changes resulting from the addition of interface elements or from the variations in the shear strength of interfaces have never been investigated. In this study, these aspects were analyzed with two-dimensional (2D) (plane-strain) numerical models. The stress changes resulting from the variation of the backfill's shear strength were also analyzed. The results show that the stresses decreased as the interfaces' shear strength increased but were relatively insensitive to the variation of the backfill's shear strength. When the interfaces have the same shear strength as the backfill, the consideration of interface elements is not necessary in numerical models because the stress distributions with or without consideration of interface elements are almost identical. When the interfaces are weaker than the backfill, the stresses obtained by the two numerical models can differ considerably, and the interface elements should be used in numerical models.