Geotechnical and geophysical assessment of the 2011 Daly Brahim landslide, in the southwest of Algiers, Algeria

Landslides are a prevalent phenomenon in the vicinity of Dely Brahim city in the Southwest of Algiers. The majority of these landslides remain active to this day, frequently occurring in the Pliocene marl formations, particularly those outcropping in the Sahel zone (coast in Arabic). These landslides result in damage to neighboring properties or public infrastructure, causing social and economic disruption or environmental degradation in most urban and coastal areas of the country. The principal objective of this study was to enhance our comprehension of the initiating processes and mechanisms of these landslides. Initially, Electrical Resistivity Tomography (ERT) was employed to monitor the behavior of electrical resistivity within the landslide area. The resulting models were then cross-checked with geotechnical data from in situ and laboratory tests. The combined interpretation of the data revealed that a potential sliding surface could be associated with a low resistivity horizon within the shallow layers of marls at a depth of approximately 9 metres. Consequently, the results indicated that the upper marl formations were generally weathered and characterized by higher water content than the deeper formations. Additionally, factors such as demographic growth and increased urbanization have contributed to the occurrence of landslides in the region.