The climate of the dry regions of the Sahara allows a wide range of materials that would be prohibited in humid to sub-humid zones of the Mediterranean regions to be used in road construction. Their deposition is guided by local geological and geomorphological conditions. The specifications for their use in road engineering take into account the geotechnical criteria relevant to climatic zonality. The materials most commonly used include the following : - Dune sands that cover an immense area that is the large Eastern and Western Ergs ; These sands are either predominantly siliceous or gypsic, or arenitic, depending on the regional geology. - The granitic or gneissic arena sands that cover a large part of the Hoggar desert. These are the product of exogenous in situ weathering of the upper part of the granitic or gneissic massif of the schistose crystalline massif. - The weathered basalts that split either in boulders or in gravel with continuous grading over aweathering thickness of 1 to 2 meters. They are associated with basalt or andesite extrusion zones of the Hoggar. These gravel are frequently used in road pavements in the Tamanrasset region. - The Zarzanitine Trias series clays in the region of In Amenas that split into sand or gravel on extraction. These are very hard and compact rock. - The plateau ungraded material (plateau run). Large surfaces one covered by sand-clay-gravel surface formations. - The calcareous, gypsic or mixed incrustation commonly known as tuffs covering large areas both in the region of the Saharan Atlas and in the Saharan flats. Using case studies of major Saharan roadways and research studies carried out in different laboratories including that of the University of Algiers, we hereby present the allowable specifications relative to their use in the field of roads as well as several examples of damage that have appeared in certain road construction projects in the past thirty years. For the covering abstract see ITRD E135448.
Abstract