Structural logging and modelling for use in simulation of inflows in underground hard rock mines (2023)

Kym L Morton, Barry D Millsteed, Wayne van Heerden, Moses Msitsini

Abstract
African mines are predominately located in hard rock. Inflows to the underground or surface workings are typically along geological structures. Often the matrix permeability of the country rock is very low, individual water bearing structures provide some 80% of the inflows. It is therefore very important to map geological structures and plot the sources of water flowing into the mine.
Fractured rock aquifers have very distinct anisotropy and in Southern Africa, North – South striking structures are usually tensional, carrying most of the water into a mine. East-West structures tend to be compressional because of the plate tectonic regime and can be barriers to groundwater flow.
Permeability is proportional to aperture cubed, therefore, the width, vertical and lateral extent of the apertures in the water bearing geological structures are important to know for use in inflow calculations.
Accurate logging of core and underground or in-pit structural mapping is essential to understand the direction and risks of inflows to mine workings in both the short term and for life of mine. This paper describes the occurrence of fracture-controlled flow in mines, methods of mapping, logging and use in mine inflow simulations.
Keywords: Structural mapping, inflows, dewatering, faults, boundaries, compartments

Morton, K.L., Millsteed, B.D., van Heerden, W.L., Carow, A. & Msitsini, M. (2023) ‘Structural logging and modelling for use in simulation of inflows in underground hard rock mines’, in Stanley, P., Wolkersdorfer, C., Wolkersdorfer, K. & Mugova, E. (eds.) IMWA 2023 – Y Dyfodol | The Future, Newport, Wales, UK: International Mine Water Association, pp. 365–370.