This dissertation will explore the process followed in the design of a sub-level open stope (SLOS) by using examples of actual stopes scheduled to be in production between August 2006 and February 2007. The main objective is to give the reader an understanding into sub-level open stoping and the design process followed. The objective here is to present a design methodology applicable to sublevel open stoping, but also to then bridge the gap between theory and practice by applying said methodology to an actual design example. The design examples used in this dissertation is based on the O640, L651 and N659 stopes in the 3000 Orebody of Xstrata Copper Operation’s Mount Isa Mine, located in North-West Queensland, Australia. The actual design reports as required by the mine are attached in Annexure 1 through 3. Given the similarities of the designs, only O640 will be analysed comprehensively within the main content of this report, with L651 and N659 discussed specifically insofar issues that were unique to these stopes. With the design of O640, all aspects or design considerations as stipulated in the design process were discussed and analysed so as to define the final stope shape. These design considerations include: <ul> <li> Faulting</li> <li> Grade Contours</li> <li> Existing Development</li> <li> Surrounding Fill masses</li> <li> Rock Mechanics</li> </ul> Once the the final stope shape has been set, options regarding stope extraction will take place. This is where the initial stope layout takes place and where the engineer looks at the advantages and disadvantages of all the different options available in mining the stope. In this phase, the most effective extraction option is decided upon. Once the engineer have decided a final stope shape and extraction option, the stope will be analysed in further detail referring to drilling, the amount of drawpoints, ventilation and other stoping requirements. These are all defined as stope design features and are considered a general summary of the stope design. The design features phase is closely followed with all the safety considerations that have been taken into account since the stope design started. Main concerns and stope specific safety issues are discussed and possible solutions given. It is part of the work of the mine planning engineer to anticipate all possible safety issues and make the production department aware of what can be expected during the development, mining and filling activities of every stope. At this stage the design of the stope nears completion. The remainder of the design now goes into more detail and addresses the critical tasks that from part of sub-level open stoping. These include: <ul> <li> Reserves and Scheduling</li> <li> Development and Drilling</li> <li> Production and Firing (Blasting)</li> <li> Ventilation</li> <li> Services</li> <li> Filling</li> <li> Economic Analysis</li> </ul> Although all of the abovementioned have already been mentioned during the design features phase, it is still required to give additional details so the different departments involved have an accurate idea of what to expect, when to expect it and therefore be able to sufficiently plan for it. It must be noted that it does happen that something may be “discovered” during any stage of the final design, which may render the current design undesirable. When this happens the stope must be re-designed until all issues have been resolved or at the least have been managed appropriately. Even though this report does not go into detail with the L651 and N659 designs, these designs are included as they bring to light issues that may arise that are unique to individual stopes. L651 looks at how a design drastically changes when ore not planned for is discovered. N659 looks at what happens when a stope is the first to be mined in an area with inadequate infrastructure. The main content of the dissertation discusses and explains the design procedure as it would take place at Mount Isa Mines, but it is still quite difficult to follow logically. For this reason a flowchart was included to give the reader a more comprehensive summary of the design process. / Dissertation (MEng)--University of Pretoria, 2011. / Mining Engineering / unrestricted

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).

This thesis presents the results of open stope stability and dilution research which focused on evaluating and quantifying stress, undercutting, blasting and exposure time and their effect on open stope stability and dilution. Open stope mining is the most common method of underground mining in Canada. Unplanned stope dilution is a major cost factor for many mining operations. Significant advances in empirical stability and dilution design methods have improved our ability to predict probable dilution from open stoping operations. However, some of the factors that influence hanging wall dilution are either ignored or assessed in purely subjective terms in existing designs. This thesis attempts to quantify these factors, from a geomechanics perspective, to assist in predicting and minimizing dilution. A comprehensive database was established for this study based on two summers of field work. Site geomechanics rock mass mapping and classification were conducted and case histories were collected from Cavity Monitoring System (CMS) surveyed stopes from Hudson Bay Mining and Smelting Co. Ltd. (HBMS) operations. The stope hanging wall (HW) zone of stress relaxation was quantified based on extensive 2D and 3D numerical modelling. Stress relaxation was linked to the stope geometry and the degree of adjacent mining activity. The influence of undercutting on stope HW stability and dilution was analysed using the case histories collected from HBMS mines. An undercutting factor (UF) was developed to account for the undercutting influence on stope HW dilution. Numerical simulations were conducted to provide a theoretical basis for the undercutting factor. A relationship was observed between the degree of undercutting, expressed by the UF term and the measured dilution. Many factors can significantly and simultaneously affect a blast performance, which may result in blast damage to stope walls. Major blasting factors which influence stope HW stability were identified. The influence of blasting on stope HW stability and dilution was evaluated based on the established database. The HBMS database, Bieniawskis stand-up time graph, as well as Geco mine case histories were used to evaluate the influence of exposure time on stope stability and dilution. Relating increased mining time to increased dilution allows the mining engineer to equate mining delays to dilution costs. Each of the factors assessed in this study was studied independently to assess its influence on stope dilution, based on the HBMS database. The factors influencing dilution often work together, so a multiple parameter regression model was used to analyze the available parameters in the HBMS database. The findings of this research greatly improve an engineers ability to understand and to predict the influence of mining activities and stoping plans on hanging wall dilution.

This thesis presents the results of open stope stability and dilution research which focused on evaluating and quantifying stress, undercutting, blasting and exposure time and their effect on open stope stability and dilution. Open stope mining is the most common method of underground mining in Canada. Unplanned stope dilution is a major cost factor for many mining operations. Significant advances in empirical stability and dilution design methods have improved our ability to predict probable dilution from open stoping operations. However, some of the factors that influence hanging wall dilution are either ignored or assessed in purely subjective terms in existing designs. This thesis attempts to quantify these factors, from a geomechanics perspective, to assist in predicting and minimizing dilution. A comprehensive database was established for this study based on two summers of field work. Site geomechanics rock mass mapping and classification were conducted and case histories were collected from Cavity Monitoring System (CMS) surveyed stopes from Hudson Bay Mining and Smelting Co. Ltd. (HBMS) operations. The stope hanging wall (HW) zone of stress relaxation was quantified based on extensive 2D and 3D numerical modelling. Stress relaxation was linked to the stope geometry and the degree of adjacent mining activity. The influence of undercutting on stope HW stability and dilution was analysed using the case histories collected from HBMS mines. An undercutting factor (UF) was developed to account for the undercutting influence on stope HW dilution. Numerical simulations were conducted to provide a theoretical basis for the undercutting factor. A relationship was observed between the degree of undercutting, expressed by the UF term and the measured dilution. Many factors can significantly and simultaneously affect a blast performance, which may result in blast damage to stope walls. Major blasting factors which influence stope HW stability were identified. The influence of blasting on stope HW stability and dilution was evaluated based on the established database. The HBMS database, Bieniawskis stand-up time graph, as well as Geco mine case histories were used to evaluate the influence of exposure time on stope stability and dilution. Relating increased mining time to increased dilution allows the mining engineer to equate mining delays to dilution costs. Each of the factors assessed in this study was studied independently to assess its influence on stope dilution, based on the HBMS database. The factors influencing dilution often work together, so a multiple parameter regression model was used to analyze the available parameters in the HBMS database. The findings of this research greatly improve an engineers ability to understand and to predict the influence of mining activities and stoping plans on hanging wall dilution.

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).

Empirical design methods are commonly used for rock mechanics evaluations. An appropriate method of rock mass classification is required to use these empirical methods. There are limitations for rock mass classification methods when access to the ore zone is restricted. The Cameco Corporation Eagle Point Mine in northern Saskatchewan, Canada, uses the longhole open stope mining method for the recovery of uranium ore. The Modified Dilution graph is used for the prediction of stope hanging wall dilution. The mine currently uses a rock mass classification based on an estimate of the alteration and strength of a rock mass from geological drift mapping. Since this method is highly subjective, point load testing of diamond drill hole core was completed to attempt to correlate the alteration and strength of different rock types to remove the user subjectivity. The results of the testing indicated a general trend of decreasing rock strength with increasing alteration, albeit with considerable scatter. A repeatable, standardized method of evaluating the stope geometry and inferred rock mass classification for reconciliation purposes was developed. The standardized stope evaluation method removes significant subjectivity currently involved in estimates of stope geometries and the magnitude of dilution. A new lithology based method for interpreting the mine specific geological alteration and strength classification system was developed based on several sources of rock mass classification observations. This resulted in a correlation linking individual rock mass property descriptions between different classification systems for an improved estimate of the Q’ classification value. This improved method of estimating the rock classification Q’ value, as well as conventional techniques for linking classification systems, was used in a stope reconciliation process to predict open stope dilution. Twenty-seven stope reconciliation case histories were documented and used to compare predicted and measured dilution, based on three different approaches for estimating rock mass classification values. The results showed a minor improvement in dilution prediction using the approach developed in this study. The systematic stope reconciliation and rock mass classification approach did highlight areas in the weak pegmatoidal rocks where improved rock classification estimates should be investigated.