Design of an optimal open pit layout for Tiira gold mine using geotechnical properties.

Abstract

Geotechnical properties play an important role in the stability of any excavation in mines. This makes it an important factor of considering in order for safety to be realized to enhance operation in mines. Tiira Gold Mine is a surface and underground mine located in Busia district in Eastern Uganda at approximately 200 km east of the capital, Kampala. The Company's office is six kilometres northwest of Busia town at about 34000 'E, (UTM 616500E and 56700N). Boniface pit is the current operational open pit with about 2 benches, pit height of 15m. bench width of about 10m, bench height of 5m, bench angle of 800 and the angle of repose of overburden is 600. The pit however is not stable to support further operation due to no proper design thus having a risk. of being abandoned for the sake of safety. This open pit mine has been designed to maximize safety and productivity. The. study was conducted basing on several analysis both from the field and laboratory to come up with an optimal design. The findings indicated that the surface rock mass of Tiira mine is very weak with a uniaxial compressive Strength of about 10.234MPa, shear strength of about 10.459MPa, the genera] rock quality being 24.335% and a rock mass rating This indicates that for the rock to be excavated using open pit method, the slope angle should be relatively smaller and the bench sh0fÆId be wider to enhance safety for the practitioners and equipment, The open pit design was designed with a bench angle of'600 and an overall slope angle of 320 having a ditch that extends 2.89m on the exposed surface and 3m deep to provide a water collection point at every level of operation. Safety was also increased with the. FOS of the pit being 3.21.