Geometrica and Carlos Caballero SRL have created a rugged solution high in the Bolivian Altiplano. Located at over 4,000 m above sea level, San Cristobal is the largest mine in Bolivia. The open-pit silver, lead and zinc mine moves 150,000 t/d of rock, and processes 40,000 t/d of ore. The dome protects workers, the environment and neighbouring communities from the release of dust from its stockpile, and protects the material awaiting transport to the ore processing facility.In early 2010, Bolivian contractor Carlos Caballero SRL responded to a bid request for a stockpile containment solution. Caballero teamed with global storage company Geometrica to propose a customised containment solution for the mine. Following review of the proposal and visits to other Geometrica 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 a Geometrica 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 Geometrica dome 140 m in diameter and 59 m in height anchored by concrete foundation — the largest dome of its kind in South America, the companies report. The foundation, which accommodates a 9 m change in elevation over 140 m, is fitted to the terrain. The dome is designed to withstand wind speeds of up to 150 km/h and an ice load of 110 kg/m2.
San Cristobal’s Geometrica dome is made up of more than 88,000 galvanized steel tubes organised and inserted into aluminum hubs to form the structure. Local crews recruited by Caballero built the dome as deliveries by Geometrica arrived on site. Shipments consisted of containerised crates of parts, each holding 2 t of structure, and organised by construction phase. The Geometrica 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.
A ventilation lantern is located at the top of the dome and the side of the dome can support dust removal equipment. The interior includes a system for lowering the material-conveyor pulley for maintenance, and a catwalk circling the dome interior. Three 13 m x 10 m doors allow simultaneous access by up to two off-road vehicles to the interior of the dome. The finished building is clad in galvanised and painted metal sheets and translucent skylights provide natural light. Material is transported from the dome to the ore processing plant via an existing underground tunnel.
- Covered area 15,493 m2
- Surface area 25,340 m2
- Base diameter 143 m
- Height from base to apex of dome 59 m
- Weight of structural dome elements 523,400 kg
- Structural material – galvanised steel and aluminium
- Number of tubes – 88,329 pieces
- Number of connectors – 25,295 pieces
- Cladding – galvanised steel, painted steel and translucent panels.
Geometrica says that “in addition to creating the largest bulk storage dome in South America at San Cristobal, [it] has designed more than 15 bulk storage domes for mining projects located in the Andes, where construction challenges include rugged terrain, remote jobsites and high snow loads. Examples of recent projects include the Barrick Zaldivar mine, the Mantos Blancos copper mine, both located in neighbouring Chile, as well as Minera Aguas Tenidas in Spain. Hundreds of Geometrica structures have been built for clients and end users around the world including BHP Billiton, Anglo-American, Barrick, Codelco, First Quantum, Fluor, Sumitomo, and other mining companies in locations ranging from the Sahara desert to the jungles of Borneo.
In addition to the solutions for irregular shapes, Geometrica offers containment solutions for automated, ring-shaped stockpiles and for spans of up to 300 m. A precise design process, the ability to package and ship a complete structure by construction phase, and mechanical structural joints that do not require welding result in a durable structure that is easily built in a wide range of environments.