A geotechnical survey and a stability assessment of the Erdenet open pit mine walls, Mongolia

The comprehensive geotechnical survey of the open pit mine Erdenetuin Ovoo in Mongolia comprised a wide range of activities whether on site, or subsequently in the evaluation of acquired knowledge. The site of Erdenet represents one of the largest copper-bearing deposits of the “porphyry copper” type in the world and its discovery is very much due to the Czech geologist E. Komínek. The work performed thus follows the preceding work of Czech geologists, who have gained a good reputation in that country. The deposit itself lies close to the town of Erdenet and is formed by a stockwork of an irregular shape 3,000 m long and 500-1,500 m wide. The surrounding rocks are largely represented by granodiorite and porphyry with younger veiny penetrations of andesite, rhyolite and other rocks.

Fieldwork comprised drilling together with the description of drill core and rock sampling, the documentation of the mine walls focused on data collection for stability calculations and remote mapping using a drone. Tests for identifying the physical and mechanical properties of rocks were carried out in the laboratories (among others, also deformation tests for measuring deformation moduli, triaxial tests or shear tests on inclined matrices). The acquired data were evaluated and, using them, a geotechnical model of the site was constructed and the properties of each rock were determined. Subsequently, the calculations of the stability of the mine walls were made, both in the existing shape and in the future final shape of barrier walls. The activities mentioned above provided data for fulfilling the assignment, which was to verify the feasibility of the plan to deepen the mine to a depth of 500 m and to recommend a particular measure for safe and effective mining.