Substantial capacity enhancement of mines in the Copper Belt of Zambia has required that geotechnical expertise and innovative solutions be applied while sinking new shafts from surface through sub soil (saprolitic) and incompetent rock to a considerable depth. One shaft is now in operation and boasts the tallest steel headgear in the south hemisphere.

The surface geology of the area exposes typical sub-tropical soils where the upper 25 to 80m consists of very weathered saprolitic soils overlying more competent granitic or conglomerate rocks. At the surface, the colluvial materials exhibit large collapse potential. Shaft sinking in these conditions is problematic, geotechnically challenging and is complicated but the high cost and time needed to ship equipment into Zambia. To complicate matters further, groundwater is common and rainfall is generally high which creates unique and fundamental geotechnical conditions.

This paper describes the geotechnical conditions on site and the unique and innovative methods used to develop the shaft infrastructure for a project that encapsulates all the major elements of geotechnical engineering while providing a practical solution.