ASANA RIVER DIVERSION DAM DESIGN AND CONSTRUCTION

Mendivil Rivas J.; Lino M.; Duque J.H.; Young J.E. · 27th International Congress on Large Dams, ICOLD 2022 (2022) · DOI: 10.1201/9781003211808-8

Resumen

Anglo American’s Quellaveco Project, located in the Province of Moquegua, in the southern part of Peru is one of the largest undeveloped copper reserves in the world. Currently under construction, the Quellaveco project requires a large infrastructure investment, including the Asana Dam. The dam was built immediately upstream of the open pit to divert the Asana River and its small tributaries through a tunnel that allows the river bypass the mine site maintaining the natural quality of the water for the communities located downstream and to protect mining operations against flooding. The highly mineralized zone surrounding the mine resulted in very challenging geological and geotechnical site conditions include a variable weathered granodiorite, an elevated alluvium deposit sandwiched into the rock mass at the left abutment, numerous joints with clay infillings, and significant faults crossing the dam foundation, ranging from 0.1 to 12 m wide. As the dam location was determined primarily by the layout of the mine and not based on optimal foundation conditions, the structure was designed to accommodate the geology and materials available for construction. This report presents the best practical solution selected for the diversion dam design, determined to be a symmetrical hardfill dam with a maximum height of 50 m, and built using 187000 m3 of hardfill mix material. The design was driven by the highly variable foundation conditions, the use of plastic colluvial materials available near to the site and the ability to construct the spillway over the body of the dam. This paper also describes how construction challenges were mitigated and the lessons learned.