Several on-site greywater treatment systems are under development including biofiltration, whose efficiency is influenced by the filter media. Therefore, the main objective of this study was to evaluate the influence ...Several on-site greywater treatment systems are under development including biofiltration, whose efficiency is influenced by the filter media. Therefore, the main objective of this study was to evaluate the influence of the type of filter media and their grain size in the removal of organic and microbial pollutants from greywater. Hence, three types of local filter media of different grain size were used for the pre-treatment of greywater. Their removal potential and clogging time were evaluated and compared. The results indicated that the type of filter media and the grain size have an influence on the elimination of organic and microbial pollution from greywater. Indeed, sand of 1 - 2 mm in size obtained the highest removal efficiencies of organic pollutants (67.35% and 78.04% for COD and BOD5 respectively) and microbial indicators (2.07, 1.77 and 2.27 log. units for E. coli, fecal coliforms and enterococci respectively). Although media of fine texture enhanced the removal efficiencies, they experienced significant clogging problems. To overcome these limitations while enhancing the removal efficiency, 1) pre-treatment stage with coarse materials followed by a treatment with finer materials or 2) the use of a combination of fine and coarse materials should be considered.展开更多
It had been suggested to use the West African Compaction Test Procedure since the early 1950’s so as to determine the CBR of gravel lateritic soils in West African countries [1]. This test procedure called West Afric...It had been suggested to use the West African Compaction Test Procedure since the early 1950’s so as to determine the CBR of gravel lateritic soils in West African countries [1]. This test procedure called West African Compaction (WAC) [2] is largely used in road construction in West African countries and had the particularity to be long and use a large amount of material. This note is the result of several comparisons between test procedures taken to determine the CBR from the WAC method to the standardized laboratory test commonly used to determine the CBR.展开更多
The southern road network covers the eastern, central and southern administrative regions;its linear network of national and provincial roads is about 5 620 km. It was the subject of a survey for the identification of...The southern road network covers the eastern, central and southern administrative regions;its linear network of national and provincial roads is about 5 620 km. It was the subject of a survey for the identification of lateritic quarries. To this effect, 144 sites have been discovered. The collected lateritic gravels were subjected to identification analyzes (Granulometry, Atterberg Limits, densimetry, water content) and geotechnical characterization tests (Proctor Modified, CBR at 95% OPM). The obtained results show that the grain size has a great percentage of gravels (>60%) followed by sand. Stones silt and clay particles are poorly represented. The samples show a high plasticity in conformity with Casagrande’s plasticity diagram. The density values of the solid particles (γ s) are quite stable in the studied area and vary between 26 and 29 KN/m3 for a natural water content comprised between 10% and 20%. The modified proctor test gives an optimal water value (Wop %) comprised between 8% and 12%. Dry density values (γ d) varied between 18 and 30 KN/m3. The bearing capacity of the materials is good (30 < CBR < 90). These results permit the recommendation of the studied materials as foundation layers of roads for traffic classes between T1-T4.展开更多
The study of the deflection due to the passage of an axle on a pavement structure has the advantage to make possible to pronounce on the portance, the rigidity and the homogeneity of this one. In the case where the al...The study of the deflection due to the passage of an axle on a pavement structure has the advantage to make possible to pronounce on the portance, the rigidity and the homogeneity of this one. In the case where the allowed axle load is not respected, surface deflection leads to premature deterioration of the roadway. In order to study the evolution of these deformations, deflection measurements were made by using the Benkelman method in the Fatick-Kaolack road in Senegal by varying the axle load with the following values: 10, 13 and 16 tons on three different zones. The results show a linear evolution of the deflection as a function of the axle load. Also, the impact of truck overloading was studied by considering different values of the axle load with comparison to the allowed axle load by using frequent types of vehicle. A numerical simulation of the Cast3M pavement was done first, in the case of an isolated single wheel with a radius of 12.5 cm, then in the case of an equivalent dual wheel with a radius of 18.1 cm for loads of 10 to 19 tons. In the same way, the pavement design software (ALIZE) is used to analyse the variation of the axle load. The results show a linear evolution of the deflection, which corroborates the measurements made in the field and those obtained by Samb (2014) with a slope coefficient equal to 1.7. Nevertheless, the case of an isolated single wheel of 12.5 cm radius is closest to the measurements with a straight line of slope coefficient equal to 1.9.展开更多
Repeated load triaxial tests were performed on five compacted gravel lateritic soils collected from different locations in Senegal: Sébikotane, Dougar, Pa Lo, Mont-Rolland and Ngoundiane. The study revealed that ...Repeated load triaxial tests were performed on five compacted gravel lateritic soils collected from different locations in Senegal: Sébikotane, Dougar, Pa Lo, Mont-Rolland and Ngoundiane. The study revealed that resilient modulus decreases with the increase of the bulk and deviatoric stress in constant confining pressure. In addition, resilient modulus increases with the percentage of cement for appreciably equal contents of moisture. This effect tends to stop for higher stress. Besides, correlations were made with some models of resilient modulus such as the Uzan-Witczack model (Witczack and Uzan, 1988 [1]) and the National Highway Research Program (NCHRP) model (2004 [2]). The study confirms that both models give very good results with the best correlations being obtained with the Uzan-Witczack model.展开更多
This study is carried out to appreciate the coarse elements influence of the gravel lateritic soils on the pavement behavior. The material involves not only the 0/20 mm granular particles considered in the specificati...This study is carried out to appreciate the coarse elements influence of the gravel lateritic soils on the pavement behavior. The material involves not only the 0/20 mm granular particles considered in the specifications and on the laboratory tests, but also all of the material that is actually used in the construction sites. Geotechnical characterization was leaned on five differentiated granular classes of 0/20;0/25;0/31.5;0/40 and 0/63 mm diameters. The sample of 0/40 mm gets the best compaction aptitude, while that of 0/31.5 mm reaches the greatest bearing strength and a good Optimum Moisture Content. According to the requirements and its bearing strengths, the material is usable up to subbase layer and its behavior depends on the grain size.展开更多
文摘Several on-site greywater treatment systems are under development including biofiltration, whose efficiency is influenced by the filter media. Therefore, the main objective of this study was to evaluate the influence of the type of filter media and their grain size in the removal of organic and microbial pollutants from greywater. Hence, three types of local filter media of different grain size were used for the pre-treatment of greywater. Their removal potential and clogging time were evaluated and compared. The results indicated that the type of filter media and the grain size have an influence on the elimination of organic and microbial pollution from greywater. Indeed, sand of 1 - 2 mm in size obtained the highest removal efficiencies of organic pollutants (67.35% and 78.04% for COD and BOD5 respectively) and microbial indicators (2.07, 1.77 and 2.27 log. units for E. coli, fecal coliforms and enterococci respectively). Although media of fine texture enhanced the removal efficiencies, they experienced significant clogging problems. To overcome these limitations while enhancing the removal efficiency, 1) pre-treatment stage with coarse materials followed by a treatment with finer materials or 2) the use of a combination of fine and coarse materials should be considered.
文摘It had been suggested to use the West African Compaction Test Procedure since the early 1950’s so as to determine the CBR of gravel lateritic soils in West African countries [1]. This test procedure called West African Compaction (WAC) [2] is largely used in road construction in West African countries and had the particularity to be long and use a large amount of material. This note is the result of several comparisons between test procedures taken to determine the CBR from the WAC method to the standardized laboratory test commonly used to determine the CBR.
文摘The southern road network covers the eastern, central and southern administrative regions;its linear network of national and provincial roads is about 5 620 km. It was the subject of a survey for the identification of lateritic quarries. To this effect, 144 sites have been discovered. The collected lateritic gravels were subjected to identification analyzes (Granulometry, Atterberg Limits, densimetry, water content) and geotechnical characterization tests (Proctor Modified, CBR at 95% OPM). The obtained results show that the grain size has a great percentage of gravels (>60%) followed by sand. Stones silt and clay particles are poorly represented. The samples show a high plasticity in conformity with Casagrande’s plasticity diagram. The density values of the solid particles (γ s) are quite stable in the studied area and vary between 26 and 29 KN/m3 for a natural water content comprised between 10% and 20%. The modified proctor test gives an optimal water value (Wop %) comprised between 8% and 12%. Dry density values (γ d) varied between 18 and 30 KN/m3. The bearing capacity of the materials is good (30 < CBR < 90). These results permit the recommendation of the studied materials as foundation layers of roads for traffic classes between T1-T4.
文摘The study of the deflection due to the passage of an axle on a pavement structure has the advantage to make possible to pronounce on the portance, the rigidity and the homogeneity of this one. In the case where the allowed axle load is not respected, surface deflection leads to premature deterioration of the roadway. In order to study the evolution of these deformations, deflection measurements were made by using the Benkelman method in the Fatick-Kaolack road in Senegal by varying the axle load with the following values: 10, 13 and 16 tons on three different zones. The results show a linear evolution of the deflection as a function of the axle load. Also, the impact of truck overloading was studied by considering different values of the axle load with comparison to the allowed axle load by using frequent types of vehicle. A numerical simulation of the Cast3M pavement was done first, in the case of an isolated single wheel with a radius of 12.5 cm, then in the case of an equivalent dual wheel with a radius of 18.1 cm for loads of 10 to 19 tons. In the same way, the pavement design software (ALIZE) is used to analyse the variation of the axle load. The results show a linear evolution of the deflection, which corroborates the measurements made in the field and those obtained by Samb (2014) with a slope coefficient equal to 1.7. Nevertheless, the case of an isolated single wheel of 12.5 cm radius is closest to the measurements with a straight line of slope coefficient equal to 1.9.
文摘Repeated load triaxial tests were performed on five compacted gravel lateritic soils collected from different locations in Senegal: Sébikotane, Dougar, Pa Lo, Mont-Rolland and Ngoundiane. The study revealed that resilient modulus decreases with the increase of the bulk and deviatoric stress in constant confining pressure. In addition, resilient modulus increases with the percentage of cement for appreciably equal contents of moisture. This effect tends to stop for higher stress. Besides, correlations were made with some models of resilient modulus such as the Uzan-Witczack model (Witczack and Uzan, 1988 [1]) and the National Highway Research Program (NCHRP) model (2004 [2]). The study confirms that both models give very good results with the best correlations being obtained with the Uzan-Witczack model.
文摘This study is carried out to appreciate the coarse elements influence of the gravel lateritic soils on the pavement behavior. The material involves not only the 0/20 mm granular particles considered in the specifications and on the laboratory tests, but also all of the material that is actually used in the construction sites. Geotechnical characterization was leaned on five differentiated granular classes of 0/20;0/25;0/31.5;0/40 and 0/63 mm diameters. The sample of 0/40 mm gets the best compaction aptitude, while that of 0/31.5 mm reaches the greatest bearing strength and a good Optimum Moisture Content. According to the requirements and its bearing strengths, the material is usable up to subbase layer and its behavior depends on the grain size.
