Operation uplift: underpinning the Nkana smelter

The system adopted was to sink piles which were made by sinking three foot diameter shafts and filling these with reinforced concrete (a pile driver could not be used). The piles were sunk on each side of the existing foundation pier and footing until these piles were firmly seated in the decomposed quartzite or granite and then the original foundation plinth was squeezed between concrete blocks cast on top of the piles, thus transferring the column load down through the piles to the good load bearing stratum below the pebbles.
The system adopted was to sink piles which were made by sinking three foot diameter shafts and filling these with reinforced concrete (a pile driver could not be used). The piles were sunk on each side of the existing foundation pier and footing until these piles were firmly seated in the decomposed quartzite or granite and then the original foundation plinth was squeezed between concrete blocks cast on top of the piles, thus transferring the column load down through the piles to the good load bearing stratum below the pebbles.