Generalized Solution for Mining Backfill Design

Underground backfill plays an important role in the mining industry, and is one of the key elements in the routine operation of many underground mines. Its main role is to improve ground stability and reduce ore dilution. Its other advantages include the reduction of surface mining waste disposal, which in turn reduces and even eliminates some problems, such as tailing dam failure or acid mine drainage (AMD), associated with mining waste management. To ensure a safe and economical backfill design, the strength of the backfill must be high enough to allow it to remain stable during the exploitation of adjacent stopes, at the very least. This minimum required strength is usually estimated using a solution proposed in the early 1980s. However, this solution includes several limitations, including the following: it assumed a zero friction angle of backfill; it neglected the surcharge on top of the exposed backfill; it assumed an equivalency between the backfill cohesion and the bond cohesion (adherence) along the interfaces between the backfill and side walls; it neglected the shear strength contributed by friction along the interfaces between the backfill and back and side walls, as well as the shear strength contributed by cohesion along the interface between the backfill and back wall; and it assumed a high aspect ratio (height-over-width) stope. Recently, a modified solution was proposed, using the same basic approach and many of the same assumptions. In this article, the original and modified solutions are first reviewed. Further modifications are given, leading to a generalized solution that overcomes the limitations involved in the original and modified solutions. The generalized solution is validated against experimental results available in the literature. (C) 2014 American Society of Civil Engineers.