Abstract
Konkola Copper Mine’s Number 4 Shaft is a trackless underground mine applying sublevel open stoping (SLOS) mining method. Number 4 shaft wants to increase ore production from 1 million metric tonnes per annum to 3 million metric tonnes per annum in the next 5 years but ore recovery is 70% or less and dilution is 20% or more. In order to achieve the desired annual target of 3 million metric tonnes ore recovery should be increased from70% to (≥85%) and dilution should be reduced from 20% to (≤10%). Despite being one of the most used underground mining methods, the current SLOS has a challenge of high unplanned dilution. This paper reviews and evaluates parameters that influence recovery and unplanned dilution in sublevel open stopes and applies numerical modelling using PHASE2 software to establish the influence of stress environment on unplanned dilution at the mine. The input parameters for numerical modelling were: Uniaxial Compressive strength (UCS=170MPa), Geological Strength Index (GSI) =55, Young’s Modulus (E) =26000MPa, Hoek-Brown constant (s) =0.0067, Hoek-Brown constant (mi) =20 and Poisson ratio (v) =0.2 major principal stress (σ1) 39MPa, intermediate stress (σ2= 18MPa) and the minor principal stress (σ3= 15MPa). Results obtained from review of mine production records indicate that the main factors that influence unplanned dilution at Number 4 shaft are: poor ground conditions, lack of compliance to recommended stope designs, poor drilling and blasting practices, presence of geological discontinuities, adopted mining sequence of extracting high ore grade first that leads to creation of high stress blocks within the orebody and delayed mucking practice. Results obtained from PHASE 2D model indicate that total displacement of 90mm is recorded in the hangingwall hence influencing stope wall instability that leads to increased unplanned dilution. After stope extraction, it was observed that 60MPa of induced stress developed at the top right corner and 45-50 MPa at the crown pillar and right bottom corner of the stope.
Highlights
Sublevel open stoping (SLOS) is a self-supporting mining method which is widely used in the world
The main disadvantage of SLOS is that it is capital intensive and requires significant development before production can start and usually has high ground vibrations from blasts (Hartman, 1987). Another major disadvantage of sublevel open stoping is that it is associated with high unplanned dilution (Jang, 2014). (Pakalnis, 1986) Surveyed 15 mines using sublevel open stoping and found that 47% of the operations suffered more than 20% dilution
Planned dilution is the contamination within the orebody and Unplanned dilution is the contamination of ore by waste material outside the stope limit (Pakalnis et al.,1996), (Scoble and Moss, 1994), (Villaescusa, 1998), (Jang, 2014) .The term dilution is synonymous with unplanned wall dilution (Henning and Mitri, 2007)
Summary
Sublevel open stoping (SLOS) is a self-supporting mining method which is widely used in the world. The main disadvantage of SLOS is that it is capital intensive and requires significant development before production can start and usually has high ground vibrations from blasts (Hartman, 1987) Another major disadvantage of sublevel open stoping is that it is associated with high unplanned dilution (Jang, 2014). Planned dilution is the contamination within the orebody and Unplanned dilution is the contamination of ore by waste material outside the stope limit (Pakalnis et al.,1996), (Scoble and Moss, 1994), (Villaescusa, 1998), (Jang, 2014) .The term dilution is synonymous with unplanned wall dilution (Henning and Mitri, 2007). Dilution can be controlled to acceptable levels by implementation of proper mining standards (Butcher, 2000), (Ng’ambi and Mutambo, 2016)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
