Open stope hangingwall design based on general and detailed data collection in unfavourable hangingwall conditions

Abstract

This thesis presents new methods to improve open stope hangingwall (HW) design based on knowledge gained from site visits, observations, and data collection at underground mines in Canada, Australia, and Kazakhstan. The data for analysis was collected during 2 months of research at the Hudson Bay Mining and Smelting Ltd. Callinan Mine in Flin Flon, Manitoba, a few trips to the Cameco Rabbit Lake mine in northern Saskatchewan, and 3 years of research and employment at the Xstrata Zinc George Fisher mine near Mount Isa, Queensland, Australia. Other sites visited, where substantial stope stability knowledge was accessed include the Inco Thompson mines in northern Manitoba; BHP Cannington mine, Xstrata Zinc Lead Mine, and Xstrata Copper Enterprise Mine, in Queensland, Australia; and the Kazzinc Maleevskiy Mine in north-eastern Kazakhstan. An improved understanding of stability and design of open stope HWs was developed based on: 1) Three years of data collection from various rock masses and mining geometries to develop new sets of design lines for an existing HW stability assessment method; 2) The consideration of various scales of domains to examine HW rock mass behaviour and development of a new HW stability assessment method; 3) The investigation of the HW failure mechanism using analytical and numerical methods; 4) An examination of the effects of stress, undercutting, faulting, and time on stope HW stability through the presentation of observations and case histories; and 5) Innovative stope design techniques to manage predicted stope HW instability. An observational approach was used for the formulation of the new stope design methodology. To improve mine performance by reducing and/or controlling the HW rock from diluting the ore with non-economic material, the individual stope design methodology included creating vertical HWs, leaving ore skins or chocks where appropriate, and rock mass management. The work contributed to a reduction in annual dilution from 14.4% (2003) to 6.3% (2005), an increase in zinc grade from 7.4% to 8.7%, and increasing production tonnes from 2.1 to 2.6 Mt (Capes et al., 2006).