01/10/2012 | Author / Editor: Gerardo Mendez / Marcel Dröttboom
To protect their material and reduce dust creation, Minera San Cristobal covered their stockpile with a 140 metre diameter storage dome. The special construction of the storage dome allowed erection over the operating stockpile without system downtime.
Located at over 4,000 meters above sea level in the Altiplano of the Andes Mountains, the San Cristobal Mine is the largest mine in Bolivia. The open-pit silver, lead and zinc mine’s production process requires the transportation of 150,000 tonnes of rock, and the processing of 40,000 tonnes of mineral daily.
In early 2010, Bolivian contractor Carlos Caballero responded to a bid request for a stockpile containment solution. Minera San Cristobal, in accordance with its principles regarding worker protection and protection of the environment and neighbouring communities, sought to prevent the release of dust from its stockpile into the environment, and protect the material awaiting transport to the mine’s ore processing facility.
Caballero teamed with global storage company Geometrica to propose a customized containment solution for the mine. Following review of the proposal and visits to other bulk storage domes in South America by San Cristobal engineers, the project was awarded to the Caballero-Geometrica team. Caballero served as the main contractor and installer of the dome, while Geometrica, as a subcontractor, engineered, manufactured and supplied the dome. Key factors in the decision to employ this type of dome solution for the site included the team's extensive experience, the capability to build around an operating stockpile, and the capability to follow an irregular shape for the supports.
The finished stockpile containment structure is a dome 140 metre in diameter and 59 metre in height anchored by concrete foundation – the largest dome of its kind in South America. The foundation, which accommodates a 9 metre change in elevation over 140 metre, is fitted to the terrain. The dome is designed to withstand wind speeds of up to 150 kilometres per hour and an ice load of 110 kilogramme per square metre.
The Geometrica dome at San Cristobal Mine is made up of more than 88,000 galvanized steel tubes organized and inserted into aluminium hubs to form the structure. Local crews recruited by Caballero built the dome as deliveries arrived on site. Shipments consisted of containerised crates of parts, each holding two tonnes of structure, and organized by construction phase. The system requires no welding, as the prefabricated tubes slide easily into the aluminum hubs and hold fast. The precise yet simple assembly process allowed the mine to continue to operate in the midst of dome construction and made it easier to assemble the building in an environment subject to high winds.
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