Re-designing quarry slope by numerical modelling :

Abstract

Mining contributes considerably to the wealth of Uganda and the world as a whole, of which open pit quarrying has its fair share of contribution. The number of operating open mines/quarries is steadily increasing as compared to underground mines; this is due to low gestation period, higher productivity, and quick rate of investment. Open pit mining/quarrying is a mining method that involves design of rock slopes, which should remain stable for the duration of the mining. The economic impact of excessively conservative design or of failures in these slopes can be very large and every effort is required for an optimized design. slope failures of any kind, if not properly managed, can have an effect on production, result in loss of ore reserves, cause pit abandonment/premature closure of the mine, represents a safety hazard for mining personnel, which in extreme circumstances could result in loss of life. Against this backdrop, there is a strong need for good practices in slope design and management to ensure timely, suitable corrective actions to minimize the slope failures. Rock slope failures are events controlled by natural physical processes. In Uganda, most slopes designs depend on the field experience, rules of thumb with some sound engineering judgment and to a small extent using limit equilibrium and rock mass classification methods, Limit equilibrium methods deal with structurally controlled planar or wedge failures and circular or non-circular failure in homogeneous materials. Rock mass classification methods deal with the preliminary design phase when very limited rock mass data is available. The aim of the project was to apply numerical modelling in design of slopes considering different rock properties (Alzo'ubi and Alzo 'ubi 2016). Developed numerical models using FLAC SLOPE.v5.00 for finding out the factor of safety. Varied the parameters for each slope and for each had the factor of safety calculated for each step. Correlated these values with the bench parameters to find out how the factor of safety changes with changing parameters.