This dissertation describes the results of field based investigations on groundwater flow at
Ruashi Mine located in Katanga Province of Democratic Republic of Congo (DRC). The core
objectives of the study were to simulate groundwater flow, estimate flow into the pits and
ultimately design a dewatering strategy for the mine. In order to understand how groundwater
flows into and through the mine, a detailed conceptual hydrogeological model was
constructed as framework for numerical groundwater flow modelling. The numerical model
was used simulate groundwater flow and predict pit inflow volumes.
At the time of this research, mining at Ruashi was being carried out in three pits that are
expected to reach terminal depth of 180 metres below ground level (mbgl) in 16 years of
continued mining. The mine is located along a faulted overturned syncline composed of
composed of Siltstones, Argillites, Sandstones and Shales and covered by Laterite. Based on
aquifer hydraulic testing results, the transmissivity of the shallow aquifer was estimated to be
10 m2/d. The specific yield for the deep aquifer was estimated to be 1 x 10-5. The Chloride
Mass Balance Method was used to estimate recharge to the groundwater system as 280 mm
per annum (14% of Mean Annual Precipitation). Water levels vary from 1.02 to 62.5 mbgl.
The general groundwater type was analysed to be calcium-magnesium-bicarbonate (Ca-Mg-
HCO3), typical of young groundwater.
The numerical groundwater flow model area is 15.7 km2 and comprises 5 layers, 17 240
elements and 10 614 nodes. The model results indicated that groundwater flow to the pits is
unlikely to exceed 42 000 m3/d. Using the pumping capacity (15 000 m3/d) for year 2012, a
maximum water level drawdown of 55 m was estimated. However, the numerical model
demonstrated that the existing pumping boreholes can be augmented by an additional set of
16 boreholes pumping 2 000 m3/d per borehole. This pumping rate can lower the
groundwater level to about 1 188 mamsl which is about two meters below pit terminal
elevation.
This study made significant contribution to understanding the hydrogeological properties of
aquifers at the mine. The aquifer hydraulic testing data was used to estimate aquifer
hydraulic parameters. However based on the field evidence, it is suggested that Packer
testing could improve the estimates of aquifer hydraulic parameters for each aquifer. The
numerical model demonstrated the typical aquifer response to different pumping scenarios.
The different pumping scenarios were run in order to determine the optimum pumping rates
to dewater the mine.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-08082014-093641 |
| Date | 08 August 2014 |
| Creators | Chironga, Lordrif |
| Contributors | Prof G Steyl |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-08082014-093641/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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