Slope Instability along N27 National Road, Northeast Algeria

Abstract

The road landslide incidences in the northeastern mountain region of Algeria are considered as major hazard; often with huge impacts on infrastructure of highway roads causing terrible damages and significant losses. The aim of this paper is to high light; a) one of the landslide areas along the road, b) investigation carried out to characterize the ground conditions as well as geometry of sliding surfaces, c) analysis to determine the possible causes of instability, and d) potential solutions to stabilize this landslide area.

The study revealed that; the landslides occur in general in Mio-Pliocene marl and clay formations, and are mainly controlled by the climatic effect in clear relation with the rainfall episodes. The deformations of the slopes are usually happen after several drying-wetting cycles. Drying-wetting cycles result in many cracks and fissures which are the main causative factor causing slope landslides and control the characteristics of the slide surfaces. At the rainy season, the saturation of dry slope soils increases the slope soils weight as well as pore water pressure leading to increasing in shear stress and decreasing in shear strength of underlying layers and decreasing the normal stress along the created slip surfaces.

The previous low cost failed remedial works were used to control the surface rainfall water by using drainage rockfill trenches; and to support the toe of the slope by using gabions. So, the suggested more suitable remedial works in the studied area are focused mainly on strengthening the weak slope soils by using micropiles, and soil nails.