TITLE:
Effect of Water Content and Grains Size Distribution on the Characteristic Resilient Young’s Modulus (Ec) Obtained Using Anisotropic Boyce Model on Gravelly Lateritic Soils from Tropical Africa (Burkina Faso and Senegal)
AUTHORS:
Bibalo Ida Josiane Ki, Makhaly Ba, Rokhaya Gueye, Pierre Hornych, Ali Sana
KEYWORDS:
Lateritic Soil, Cyclic Triaxial with Repeated Loading (LRT), Characteristic Resilient Young’s Modulus, Anisotropic Boyce Model, Water Content, Grains Size Distribution
JOURNAL NAME:
Open Journal of Civil Engineering,
Vol.11 No.1,
March
26,
2021
ABSTRACT: This research was carried out to determine the
rheological parameters of lateritic soils in order to contribute to the
improvement of the technical documents used for pavement design in tropical
Africa. The study is based on the loading repeated of cyclic triaxial tests
(LRT) performed at University Gustave Eiffel (formerly
Institut Français des Sciences et Technologies des Transports de l’Aménagement
et des Réseaux (IFSTTAR)) in Nantes with the application of the European
standard EN 13286-7: 2004 [1]. The tests were performed at constant confinement stress and using the
stepwise method to determine the resilient axial () and radial () deformation as a
function of the axial and radial stresses. Four gravel lateritic soils from
different sites selected in Burkina Faso and Senegal were the subject of this
research for the triaxial tests. These materials have a maximum diameter of 20
mm and a percentage of fines less than 20%. The LRT tests were carried out on
samples compacted at three moisture contents (wopm - 2%, wopm and wopm + 2%) and at 95% and
100% of optimal dry density (γdopm). Test results showed that the characteristic resilient Young’s modulus
(Ec) of gravelly laterites
soils depends on the compacted water content and the variation of the grains
size distribution (sand (ø ø ø 20%), mortar and sand
(Sindia and Lam-Lam) are more sensitive to variations in water content. The
presence of water combined with the excess of fines leads to a decrease in
modulus around 25% for Lam-Lam and 20.2% for Sindia. Materials containing a low
percent of fines, mortar and sand (Badnogo and Dedougou) behave differently. And the resilient modulus increases about 225.67% for
Badnogo and 312.24% for Dedougou with the rise of the water content for
approximately unchanged the percentage of fines, mortar and sand. Granularity
therefore has an indirect influence on the resilient modulus of the lateritic
soils by controlling the effects of water on the entire system. Results of statistical
analysis and coefficients of correlation (0.659 to 0.865) showed that the
anisotropic Boyce’s model is suitable to predict the volumetric () and
deviatoric strain () with stress
path (Δq/Δp) of the lateritic soils. The predicted Er resilient Young’s modulus from anisotropic Boyce’s
model varies according to the evolution of the bulk stress (). A correlation around 0.9 is obtained from the power law
model.