Unsaturated Flow Analysis of Heap Leach Soils

Abstract

Heap leach flow patterns are governed by hydrogeological parameters including, soil properties, saturated and unsaturated hydraulic conductivity, initial degree of saturation, and the method of irrigation. Optimizing production during leaching cycles requires knowledge of the hydrogeological parameters of the leach heap, and their effect on flow behavior. This thesis research involved quantifying the flow rates of unsaturated homogenous soil profiles. Finite element numerical modeling has been utilized to simulate 1-dimensional unsaturated transient vertical flow. A series of parametric studies were conducted to examine how various soil properties and differing initial and boundary conditions affect percolation and flow. Results indicate that flow and percolation are increased or impeded based on the saturated and unsaturated parameters of the soil profile. Sensitivity analysis illustrates that the initial degree of saturation affects hydraulic behaviour relative to soil hydraulic conductivity, matric potential (negative pressure head), and the method of irrigation. At the initial stage of the research, some analyses indicated that numerical instabilities may occur within simulations due to selected mesh density, initial time step length, error tolerance, and the selected form of the unsaturated Richards Equation.