Design Criteria and Risk Management of New Construction in Landslide Areas: The Case of the Djendjen–El Eulma Highway (Algeria)

Abstract

This paper presents the approach, hereafter named “dual approach”, applied in reducing risks of roadworks-related landslides, based on the preliminary landslide assessment and the Observational Method (OM). This approach has been implemented to the design of a 110 km motorway project in Algeria, during the last 10 years. The North-South oriented alignment of this motorway crosses different environments starting from the plain area of the Djen Djen valley, passing through a very irregular and geomorphological composite area of the “Petit Kabylie” massif, up to the future connection with the existing East-West Highway. The geological context is characterized by the presence of several complex rock formations, including heterogeneous rock masses as Flysch. These rock formations are strongly deformed and weathered such that landslide occurrence can be often related to the poor unfavorable geological, structural and geotechnical conditions. Roadworks design and construction in such complex and irregular mountainous areas are faced with various and significant natural hazards including large extended landslides. The parallelism of and partial superimposition between the design and the construction phase had mainly two consequences; notwithstanding the fact it forced the timing of the two phases, on the other hand, it allowed designers to quickly update the base reference model and design choices in several cases, with significant improvements and advantages in terms of time and cost.