Determination of the Geotechnical Parameters of Tohouè Silty Sand (Semè-Kpodji) for Its Use in Road Construction in Southern Benin

Silty sands are the most abundant materials in the Littoral region of southern Benin used in road construction. These materials were once the most available in quantity and quality. Thus, this study was initiated to characterize the silty sands of Tohouè, a locality of Semè-Kpodji, for their use in road construction. To do this, an experimental study based on normative tests was used. The silty sand identification tests made it possible to determine the rate of particles with a diameter of less than 80 mm or 7.67%. The dry density is 1.95t/cm3 with a water content of 8.20% OPM, then the organic matter content equal to 0.13% with a sand equivalent of 23.07%. Similarly, the mechanical tests carried out resulted in the determination of the CBR index evaluated at 44.00% for 95% OPM with a linear swelling of 0.15%, then the cohesion whose estimated value at 95% OPM is 1.03 ± 0.25 MPa and the friction angle is 28.66˚. Thus, the pre-consolidation stress is 22.00 MPa, the shear modulus varies from 64.941 kPa to 103.848 kPa and the Poisson’s ratio varies from 0.392 to 0.484 while the oedometric modulus is 1684.91 MPa. In addition, the oedometric stress of silty sand is estimated at 58.07 MPa with a compression index of 0.046%. Similarly, the swelling index is 0.007% and the void index is 0.42%. As for Young’s modulus, it varies from 51.129 MPa to 289.110 MPa. Ultimately, the analysis of the different results in accordance with the specifications of the CEBTP 1984 guide revised in 2019 shows that silty sand can only be used as a foundation layer, regardless of the type of pavement. Finally, these studies have shown that the soil is not very compressible and over-consolidated.