Improvement of the mechanical performance of Fergoug dam sediments treated for reuse in road engineering

¹ Université de Mustapha Stambouli de MASCARA, Département de Génie Civil, Algérie
² Université de Picardie jules Verne IUT d’AMIENS, Département de Génie Civil, France

Abstract

The phenomenon of siltation is one of the main problems facing many dams throughout the world, and particularly in Algeria. The mud, before and even after extraction, is always harmful. Indeed, mud is a harmful material, first for dams, because it reduces their capacity of water storage, and second, for the environment following the desilting operations that generate large quantities of materials that occupy and sometimes pollute large areas. However, these materials can be exploited differently and used in other fields. The envisaged research work relates to real cases of silted dams, such as the dam of Fergoug (western Algeria) whose siltation rate is very high; it is estimated at 97% of its initial capacity which, according to the National Agency for Dams (Agence Nationale des Barrages - ANB), is equal to 18 million m³. The large quantities of silt extracted present an environmental problem, and its use as a local raw material for the manufacture of civil engineering materials can contribute to solve this problem. The vulnerable lands of the sub-catchment of Wadi Fergoug (Fergoug River) extend over an area of 122 km², from a total surface of 8340 km² for the dam catchment area. There is a great diversity of superficial formations with predominantly clay soils from marly formations. The rate of specific erosion has increased to 160 T/ km²/ year due to irregular annual rainfall resulting from a succession of dry and wet years. Sedimentary materials, which are found in considerable quantities, were collected at the foot of the dam, on its right bank. This study attempts to find a recycling pathway for these sediments. The objective of the present work is to investigate the behavior of silt from the dam of Fergoug (Algeria) for the purpose of using it in road construction (foundation and base layers). The method adopted is to reconstitute, in the laboratory, samples of mixtures containing road aggregates with different proportions of silt. These samples are then subjected to various tests (Normal modified Proctor, Atterberg limits, VBS, Particle size analysis, Sedimentation, DRX etc …). The results of the tests indicate that some of the prepared mixtures present very interesting properties. These results satisfy the current recommendations of the technical guides; they also corroborate their use in road construction.