Slope design at Cuajone Pit, Peru

Esteban Hormazabal, Raul Veramendi, Jorge Barrios, Gabriel Zuniga Olate, Felipe Gonzalez
2013 Proceedings of the 2013 International Symposium on Slope Stability in Open Pit Mining and Civil Engineering   unpublished
The Cuajone porphyry copper deposit is located on the western slopes of Cordillera Occidental, the southern Andes of Peru. The current pit measures about 2.5 km east-west, 3.0 km north-south, and at the end of 2012, had a maximum depth of 950 m. Mining by open pit methods commenced in 1976 and has continued since that time. Ore production is 80 ktpd. As part of the slope design program and slope optimisation, the past and present performance of the pit slopes was evaluated to provide
more » ... on the potential behaviour of future pit expansion. A geomechanical assessment is being carried out to evaluate the stability of the walls of the next expansion. To evaluate the stability of the open pit, a series of geotechnical studies have been performed. These studies involve, among others, slope stability analyses based on limit equilibrium methods and finite element numerical models. In addition, a detailed back-analysis of a five million ton failure (DSE42) was performed to calibrate rock mass properties and to understand slope behaviour in poor rock mass quality. This paper describes the back-analysis of the DSE42 failure and the slope design process for the current pit and next pushback. SPCC is currently evaluating at a feasibility engineering level the LOM for the next 15 years of mining of the Cuajone pit. The Cuajone porphyry copper deposit is located on the western slopes of Cordillera Occidental, the southern Andes of Peru (see Figure 1 ). At Cuajone Mine, the experience of past failures provides an excellent basis for design of the proposed designs. The geological and structural information gathered by the mine staff also provides good data for the confidence in design. Since there is a measure of apprehension of successful slope design implementation from past failures, back-analyses of these failures are essential to provide the level of confidence in parameters that is required to proceed with the next pushback. 2 Engineering geology Mine geology The Cuajone district exposes several thousand metres of volcanic rocks assigned by Bellido and Landa (1965) and Bellido (1979) to the Paraleque Volcanics and Quellaveco Formation of the Upper Cretaceous to Paleocene Toquepala Group. The stratigraphy will be divided into three broad categories: pre−mineralisation rocks; intrusive rocks; and post-mineralisation rocks.
doi:10.36487/acg_rep/1308_34_hormazabal fatcat:undmzjgxu5bbxc7lqvyud4the4