Developing an engineering geological model in the fractured and brecciated rocks of a copper porphyry deposit

Abstract Successful open-pit slope design depends on the formulation of a representative geotechnical model. This paper presents the development of an engineering geological rock-mass model as part of a feasibility geotechnical study for the Tampakan copper/gold open-pit mine in the Philippines. This porphyry deposit has been subjected to several cycles of volcanism, chemical alteration and tectonic disturbance resulting in a complex, highly fractured and brecciated rock mass. The model requirements for design were identified early in the project and a unique geotechnical logging system was developed to effectively capture the relevant rock-mass characteristics.