Geological Characterization and Stability Conditions of the Motorway Tunnels of Arrangement Project of the NR43, Melbou (W. Béjaïa)

Abstract

The oriental coastal region of Béjaïa city is situated in the mountainous chain of the Babors. The relief is steep as well as slopes which are very abrupt. In the North, the Babors coastal massif dominates the Mediterranean Sea forming the Cap of Aokas and Djebel Djamaa N’ sia in the city of Melbou. The recent realized tunnels (T1, T2) cross the limestone massif of Djebel Djamaa N’ sia dated of the Jurassic era, which shows an intensive deformation due to the fracturing as well as to the karstification. Several instabilities have been observed at the time of their realization. Both tunnels (T1, T2) are excavated by mining in two sections; Skullcap and stross. Basing on the geologic survey, the geotechnical interpretation and the geomechanical classification of Bieniawski are the basis for what the retaining type were stopped (Flies, anchoring bolts or the special processes for particular cases).