In-situ stress determination at Ruttan Mine, Sherritt Gordon Mines Ltd.

CIM Bulletin, Vol. 78, No. 884, 1985

R. PAKALNIS and H. MILLER, University of British Columbia, Mining and Mineral Process Engineering, Vancouver, British Columbia, T. MADILL Sherritt Gordon Mines Limited

This paper describes a methodical approach to the estimation of the orientation and the magnitude of in-situ stresses. The study was performed at the Ruttan Mine, Sherritt Gordon Mines Ltd., a 6,000 T.P.D. underground operation, located in northern Manitoba, Canada. It involves an initial estimate to be made based upon: structural interpretation virgin stress measurements conducted in other areas (world wide, regional)  The verification of the prevailing stress regime was made by conducting CSIRO hollow inclusion'1' overcoring measurements. The current cost for a virgin stress determination is about $7000per measurement'2' and the difficulty encountered in attaining a good reading is high. This paper will describe the analytical procedures employed at Ruttan in evaluating the in-situ stress magnitude and orientation based on three overcore tests. It is proposed to perform an additional six measurements in order to verify the following results:Vertical stress = av (MPa) = 0.027 by depth (m) Major principal stress = al = 2.5 xav (340°/-20°)* Intermediate principal stress = a2 ~ 1.2xov (070°/0°) Minor principal stress = a3 - O.Sxav (160°/-70°)
Keywords: Rock mechanics, In-situ Stresses, Virgin stress measurements, Structural geology, Fractures, Boreholes, Debonding, Overcoring.