Adequate drainage system design for heap leaching structures

The paper describes an optimum design of a drainage system for a heap leaching structure which has positive impacts on both mine environment and mine economics. In order to properly design a drainage system the causes of an increase in the acid level of the heap which in turn produces severe problems in the hydrometallurgy processes must be evaluated. One of the most significant negative impacts induced by an increase in the acid level within a heap structure is the increase of pore acid pressure which in turn increases the potential of a heap-slide that may endanger the mine environment. In this paper, initially the thickness of gravelly drainage layer is determined via existing empirical equations. Then by assuming that the calculated thickness is constant throughout the heap structure, an approach has been proposed to calculate the required internal diameter of the slotted polyethylene pipes which are used for auxiliary drainage purposes. In order to adequately design this diameter, the pipe's cross-sectional deformation due to stepped heap structure overburden pressure is taken into account. Finally, a design of an adequate drainage system for the heap structure 2 at Sarcheshmeh copper mine is presented and the results are compared with those calculated by exiting equations.