Geotechnical Characterization and modelling of the Mandena heavy mineral sand deposit

Biological cementation of the Mandena heavy mineral deposit in Madagascar was causing difficulty in dredge mining and hence in planning and control of production rates. An investigation was initiated to better evaluate the geotechnical properties of the orebody sands.  The investigation was aimed at defining the distribution and geotechnical properties of the cemented strata, in order to generate a site specific geotechnical model for the Mandena deposit. The geotechnical characterisation was developed using an integrated approach of sever-al ground investigation techniques such as piezocone (also known as CPTu) testing, geotechnical drilling, SPT testing as well as laboratory testing. The final outcomes of the investigation included a 3D geotechnical model showing the distribution and extent of the cemented areas as well as the typical geotechnical parameter ranges associated with each of the defined geotechnical units. The interpretations developed were incorporated into the mine and production planning to ultimately optimise operational planning and control.