Geotechnical challenges of the biggest mining project in Argentina

Pascua-Lama is the first bi-national mining project in the world, located between 3800 and 5200m.a.s.l. on the borderline between Chile and Argentina. Pascua lies on the Chilean side, in Huasco Province in the Atacama region, while Lama lies on the Argentinean side, in the Iglesia department in San Juan province. The project is developed by Barrick Gold and consists of the open-pit mine of one of the world's largest gold and silver deposits, with more than fifteen million ounces of proven and probable gold reserves and six hundred and seventy-five million ounces of silver contained within the gold reserves, as of December 31st 2013 and official reports. The project is still in the construction stage. Future production will include open-pit extraction from Chilean and Argentinean sides, primary crushing in  Pascua, transportation  of crushed  ore  to  Lama  through a 4.0km-long underground tunnel, stockpiling, processing and final disposal at the tailings dam in Lama. Site lithology can be characterized as superficial alluvial or colluvial  soils  generally  followed  by  a  competent  cemented granular  stratum named ferricrete which lies on top of a highly resistant igneous bedrock, mainly andesite, diorite and dacite. The paper describes the design and construction of some of the excavations, foundations, slopes, fills, retaining walls, MSE walls and CLSM  fills,  and  the  challenges  imposed  by  high  altitude,  steep  landscape, extremely cold winter temperatures and the complexity of the construction site.