Doubling of Aokas tunnel (Bejaia): geology and geotechnical characterization of solid crosses. Stability of the structure

• Published in: Bulletin of engineering geology and the environment 2013-12, Vol.72 (3), p.477-483
• Main Authors: Hallal, Nassim, Bougdal, Rachid, Bensafia, Wahiba
• Format: Article
• Language: English
• Subjects: Chains; Geology; Geotechnics; Reinforcement; Rock; Stability; Tunnels (transportation); Underground
• ISSN: 1435-9529; 1435-9537
• DOI: 10.1007/s10064-013-0508-1

Underground workas constructions and design techniques depend closely on the geological environment. The properties of the rock mass influence directly on the various steps of their realization so that geological and geotechnical studies become an absolute necessity to characterize the rock mass and to control the imposed constraints. At the end, we can conclude that the present work aims to define the geological and geotechnical conditions of the drilled rock mass; it consists mainly in determining the nature and the structure of the rock mass to cross, in addition to determining the rock mass stability and the reinforcement works. The route of the tunnel Aokas (Bejaia) crosses a fractured limestone, where the karstification phenomenon is well developed and the best example being afairy cavesa contiguous on the old tunnel road in the NR 09. The two tunnel heads are located at the foot of two towering cliffs. All these characteristics make the tunnel in precarious potential stability. The detailed geological study allowed to determinate that the tunnel crosses through a karstified dolomitic limestone of the Baboras chain of the lower Jurassic age, and a geotechnical study allowed a characterization of this rock mass regarding fracturing, mechanical and physical characteristics and led finally to a geomechanical classification. The stability of the tunnel is ensured by a strong support system.