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Client

Erudite

Location

Northern Zambia

Project Description

The Mimbula Copper Mine extracts copper-rich oxide and sulphide deposits from a site located on the outskirts of the town of Chingola in Zambia. The mine is owned and operated by Moxico Resources PLC, and the copper ore is currently hauled and processed at the KCM TLP to produce LME Grade A copper cathode.

Plans to construct a processing plant at the mine are underway to decrease haulage costs and external processing. The new processing plant will host five new thickener tanks.

A detailed settlement analysis was conducted for the new planned thickener structures at the Mimbula Copper Mine in northern Zambia. The brief was to predict the settlement that can be expected underneath the soil embankment which will serve as the founding strata for the new thickener tanks.

Project Tasks

  • The total expected settlement is the sum of the immediate (elastic) settlement and consolidation settlement. The elastic settlements would primarily occur during the construction phase, while consolidation settlements may take many months or even years to realise.
  • The time taken for the consolidation settlement to occur depends on the coefficient of consolidation (Cv), which is a function of the material’s permeability. No consolidation tests results were available and thus, assumptions for consolidation parameters had to be made based on relevant literature.
  • The settlement and consolidation analyses were conducted using Rocscience’s Settle3 v5.017 software. The embankment and tanker construction process were replicated in the Settle3 model using a stage-based method, where different stages constituted a construction stage.
  • Three different scenarios were considered: 1) Sc1: No Ground Improvement 2) Sc2: Ground Improvement (remove and replace) top 5.0m 3) Sc3: Ground Improvement (remove and replace) top 7.0m.

Project Results

The in-situ geological profile showed approximately 10m of low plasticity (CL) soft clays, which resulted in approximate total settlements of between 100-320mm during each construction phase, i.e., construction of embankment followed by the construction and operation of the tankers. To reduce these settlements, a soil replacement technique involving the removal of the soft clays and replacing these with engineered fill was investigated. Two scenarios were considered where 5m and 7m of the soft clays were removed and replaced. The analyses showed that the settlements could be reduced by nearly 50%, depending on the amount of in situ material replaced.

Additionally, the client was impressed by the visuals and representations of the models and by incorporating Settle 3 extensive library on consolidation parameters, we were able to verify our assumptions for the consolidation parameters.

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