Tasiast open-pit gold mine, Mauritanian desert: the mining company KINROSS needed a retaining tip wall requiring two wing walls of 32.5m. To meet such a design requirement, the mine operator, AUSENCO, turned to Maccaferri for a cost-effective and flexible reinforced MSE wall system.
AUSENCO was providing Engineering, Procurement and Construction Management (EPCM) services for a new front-end processing facility and increasing capacity in the existing ball milling, CIL, elution circuits and tailings management system. To meet this project needs, AUSENCO chose Maccaferri’s Terramesh®, because of this system performance as well as the technical support and the design solutions provided by Maccaferri. The result was the tallest MSE Terramesh® wall of the mining sector.
Maccaferri renowned Terramesh® is a modular system used to form rock-faced reinforced soil walls and embankment. It consists of pre-assembled units of double-twisted wire mesh with polymer coating, Such protection that is very resistant to corrosion can ensure 120-year service life. The facing section of the unit is formed by connecting a back panel and diaphragms to the main fascia unit, thus creating the rectangular shaped cells used for stone confinement. Terramesh® System units are supplied in standard lengths, requiring no cuts on site. Following assembly on site, the fascia unit is filled with suitable gabion stone fill. Structural backfill is then placed upon the soil reinforcement geogrids and compacted.
The design of this structure was carried out by Maccaferri’s technical department using the MACSTARS internal slope stability software to define the length, spacing and type of reinforcement. The construction of a support structure of such a dimension requires a careful erection of the structures and a strict respect of the works procedure. MACCAFERRI submitted a complete works procedure to assist the company in all stages of the work. In addition, Maccaferri provided an engineer for three week-long on-site actions to assist AUSENCO during the erection phase. These interventions allowed for Gabions installation and setting up of the back embankment. Moreover, the gabion facing section have been installed pursuant to NFP 94-325-1 standard which defines the steps of gabion filling. Gabions were filled with the stones extracted and crushed on site. Nearly 4,000t of stones were used to fill the cages. Considering an average gold concentration of 5g/t of extracted stones, the wall consists of about 20kg of gold.
Following some of the advantages provided by choosing Maccaferri’s solutions:
- Flexibility: Terramesh® allows for settlement and consolidation without major deformation and structural implications
- Corrosion-resistance: the long-lasting polymer coating ensures protection of the wire mesh against degradation from the harsh filling soils and environmental factors. In addition, Maccaferri’s high performance Paralink® 300 and Paralink® 400 geogrids, with tensile strengths of 300kN/m and 400kN/m respectively, have been combined with the 20m-long wire mesh in the backfill to provide the reinforcement required to carry out the embankment
- Easy and fast installation: Terramesh® units are supplied in standard lengths requiring no cuts on site, saving time during installation. Besides, no specialised equipment is required for lifting units into position as all of the materials supplied are compacted and not excessive eight
- Environmental friendliness: soil reinforcement using geogrids enables the reuse of on-site materials as structural backfill to the reinforced soil structures, reducing the environmental impact of importing material and transport costs
- Local job creation: the installation of the Terramesh® units requires minimal skilled labour thus contributing to local job creation
In conclusion, Maccaferri reinforced soil solution can offer advantages for mining industry such as overall cost reduction, reliability and improved flexibility.