Geophysical characterization of the large-scale internal structure of a waste rock pile from a hard rock mine

A geophysical investigation was conducted on a waste rock pile of a polymetallic mine to define its internal structure. Three different areas of the pile were investigated using electrical resistivity imaging, ground penetrating radar, and electromagnetic conductivity techniques. The surveys were conducted on the top of the pile, along the slope of the upper bench and in several boreholes drilled into the pile. Laboratory testing was also undertaken on samples taken from three exploratory trenches dug into the top surface in order to ascertain their geochemical and hydrogeological properties. The geophysical surveys indicated a general horizontal layering in the core of the pile and dipping stratification parallel to the slope along the edges. These features are related to the method of construction and, to a lesser extent, to a change in the waste rock characteristics. Integrating all the data confirmed that such geophysical investigations can provide valuable information to assess the internal structure of a waste rock pile. The ensuing structural model can then be used to construct a hydrogeological model which can form a basis for evaluating the flow of water (and gas) in the pile.