Design of stable open stope using empirical and numerical methods for Barrick Gold Mali (BGM)

Abstract

The Gara Mine (GM) of Barrick Gold Mali uses longitudinal sublevel open stope mining method. At the current depth of 653 m, GM is facing stope stability problems. The objectives of this research were set to determine the dimensions of stable stopes and hence design a stable stope. Secondary data consisting of rock mass characteristics, geotechnical mapping data and rock sample test data were used in this research. Numerical and empirical methods were used in conducting the analysis of this research. Boundary Element Method (BEM), which is a numerical method, was used to evaluate the induced stresses and to classify stress types of the stope faces. After the BEM was conducted, it was revealed that the stope faces exhibited different states of stresses, namely compression and tension; Although not all the faces exhibited tension while the structural analysis of the data showed two critical joints at both the south and north of stopes of GM. The empirical method was used to determine the stable stope geometry using Hani’s Maximum Stress Factor (A') which is a modification to Potvin Stress Factor (A) due to the revelation of the absence of tension in some of the stopes. It was recommended that the stable stopes should have a maximum length and height of 29 m and 25 m respectively. Another recommendation made was that GM should be mindful of the two critical joints observed so that the stope strike and joint dip do not contribute to rockfalls in the stope. Lastly, Hani’s Maximum Stress Factor has been recommended for use in determining the stress in stopes faces under tension while, the Potvin’s Stress Factor could be used in determine the stress in stope faces under compression.