A new technique for prediction of spoilpile stability: case history at the Kara Kara strip mine, Guyana, South America

CIM Bulletin, Vol. 76, No. 857, 1983

H. GEORGE and D.F. VanDINE, Department of Geological Sciences (Engineering), Queen's University, Kingston, Ontario

The possibility of spoilpile failure at the Kara Kara bauxite strip mine, Guyana, South America, is of major concern to the mine operators. The current mining technique requires the continuous operation of an 11 m3 bucket capacity walking dragline on top of 18 metres of freshly spoiled uncompacted overburden material consisting of varying mixtures of kaolinitic clay and quartzitic sand. A field biased geotechnical study of undisturbed overburden and corresponding spoiled material has identified site-specific, non-linear correlations between vane shear strength, standard penetration resistance and spoilpile composition. Readily available geological exploration borehole logs has enabled a composite clay isopach map of the entire mining property to be drawn and critical areas to be zoned according to expected slope stability. Stability has been assessed using simple hand calculation techniques. Use of the resulting stability map provides the mine operators with a means of forecasting the need for appropriate preven-tative measures at varying stages of mine development, throughout the life of the mine. A similar investigation procedure could be employed at many presently operating and future strip mines.
Keywords: Spoilpile, Slope stability, Prediction, Shear strength, Dragline, Strip mine, Overburden, Standard Penetration Test, Pull-back, Vane Shear Test.