A multi criterion approach for the selection of optimal bench width in open pit mines

Open pit design has to address the stability of benches, inter ramp and the global stability of the pit walls. Benches are required to provide a safe working environment for personnel and equipment. Limit equilibrium techniques based on available geomechanical data are used to design safe face slope angles and bench heights. A further consideration is the choice of an appropriate catch basin and bench width. It is expected that a bench should be wide enough to contain any instability from the benches above. This paper addresses the selection of minimum bench width based on legislation, company policy, operating practice and a series of technical criteria. A case study from a mining project in the Canadian arctic is employed to illustrate that the choice of any design criterion can lead to different recommendations. This paper presents systematic multi-criterion based approach that can lead to a more reliable and informed design of optimal bench width in open pit mines