Abstract
Primary Stope Back Failure in a New Mining Front at Vale’s Manitoba Operations – A Case Study
Matthew Violot and Jack Bauer
Vale Canada Ltd, Thompson, Manitoba, Canada
Vale’s Manitoba Operations Thompson Mine is located in Northern Manitoba approximately 700km North of Winnipeg. It consists of two operating underground mines (T1 and T3) that primarily extract Nickel Ore using Open Stoping and Cut and Fill mining methods. The open stoping method employed at Thompson Mine is referred to as Vertical Block Mining (VBM). Stopes are typically 30m in height with a 15m span along strike and vary in length depending on orebody thickness. Stopes are typically mined using a primary-secondary extraction sequence.
Production at T3 Mine recently initiated a new mining front that extends from 1420 to 1500 metre depth. Following the extraction of two VBM stopes in the area, the back of an adjacent primary stope failed while a third stope was in the preparation stage. The failure extended approximately 25m above the stope back before reaching a stable orientation/geometry. This presentation will present the causes of the back failure along with some of the design and operational practices which likely have influenced unfavourable ground conditions. Although design and operational factors are difficult to quantify in geotechnical stability assessments, it is important that they are considered during the design, execution, and reconciliation phases of open stope extraction to mitigate impacts on stope stability.