Multi-method Geotechnical Assessment of the 7 September 2022 Landslide at Kef Essnoun Phosphate Mine, Algeria

This study investigates the causes and mechanisms behind a recent landslide event on 7 September 2022 at the Kef Essnoun open-pit mine in North-East Algeria, a significant site holding approximately 50% of the Algerian natural reserves in phosphate. In order to evaluate the circumstances leading to the slope failure, the study was conducted using a multi-technique analysis approach, combining field observations, rock mechanics classification systems, kinematic equilibrium analysis, and a back analysis using different limit equilibrium methods to assess the conditions that caused the slope failure. The kinematic analysis using contoured stereonets through Dips software, along with the rock classification systems, suggested that a non-linear sliding would occur in the marl strata. Furthermore, the limit equilibrium analysis using Slide 2D software indicated that the sliding would occur in the marl strata and the upper part of the phosphate. The predicted slip surface closely matched the field investigations. The obtained results can help mitigate potential risks on a local and international scale in mine projects.