Experimental study of sulfuric acid effects on hydro-mechanical properties of oxide copper heap soils

Several mechanisms contribute to changes in the performance of oxide copper heaps. These include physical, biological, chemical and thermal interactions between sulfuric acid and the formation of soil particles. A series of experimental studies was conducted by simulating the column leaching process in the laboratory. The leaching of selected gravel and crushed copper oxide ores from two copper mines was carried out to measure their permeability and strength. The influence of effective parameters on gravel clogging was studied and the clogging coefficient was estimated with time. Furthermore, the ratio of particle reduction (RPR) caused by acid seepage was evaluated and an equation for the internal friction angle of ore particles over time was generated. The present study shows significant reductions of gravel permeability (28% after five months leaching) and friction angle of ore particles (25% after eight months leaching). The effects of sulfuric acid flow on the hydro-mechanical properties of oxide copper heap soils could enhance the accuracy of slope stability design and drainage layers design in industrial heap leaching systems.