The largest storage dome in South America, constructed over an operating stockpile

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 tons of rock, and the processing of 40,000 tons of mineral daily.

In early 2010, Bolivian contractor Carlos Caballero SRL 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 neighboring 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, Inc. to propose a customized 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 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 kph and an ice load of 110 kg per square meter.

The Geometrica dome at San Cristobal Mine is made up of more than 88,000 galvanized steel tubes organized 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 containerized crates of parts, each holding 2t of structure, and organized 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 additional armature on 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 galvanized and painted metal sheets and translucent skylights provide natural light. Material is transported from the dome to the mine’s ore processing plant via an existing underground tunnel.

In addition to creating the largest bulk storage dome in South America at the San Cristobal Mine, Geometrica has designed more than 15 bulk storage domes for mining projects located in the Andes, where construction challenges include rugged terrain, remote jobsites and insanely high snow loads. Examples of recent projects include the Barrick Zaldivar Mine, the Mantos Blancos copper mine, both located in neighboring 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.

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