Pavement dimensioning with and on lateritic materials of the Mbu–Baforchu area

摘要

The present study was conducted on lateritic sub-grade soils with the pavement structure built using lateritic materials.The objective of this work was to characterize the lateritic materials and obtain a correlation between the modulus of elasticity(E_(dyn)) and the Californian bearing ratio (CBR) around the Mbu–Baforchu area in a bid to dimension a second accesshighway to the city of Bamenda. Identification tests (water content, particle size analysis, Atterberg limits) and mechanicalcharacteristics tests (Modified Proctor, CBR and simple compression) were carried out on soil samples taken from thefield. The CBR results were variable with values between 32 and 49 for burrow materials, while those for sub-grade varybetween 6.5 and 14.4. A regression equation between the E_(dyn) and CBR for the burrow material gave E_(dyn)= 155.8exp (0.0541CBR) with a regression coefficient of 0.9599 while that for the sub-grade material was E_(dyn) = 69.064exp (0.0706CBR) with a regression coefficient of 0.9295. The burrow and sub-grade soils fall within the S3 and S5 soil classes respectively.The HRB classification pits the burrow materials in the A-2 class with a group indices varying between 0 and 6, whichdescribes them as a clayey loamy soils with (compressible nodular silty sands), while the sub-grade soils falls in theA-7-5 class and having variable group indices (12–20), thereby characterizing them as inorganic clays of high plasticity.The pavement structure designed for consists of a bituminous cover of 5 cm, a base course of 20 cm and a sub-basecourse of 20 cm. The pavement structure can carry a traffic loading of up to 3000 vehicles per day, inducing stresses anddeflections within the pavement structure which are lower than their required permissible values. With ε_t = − 14.5 μdef,ε_(t, perm) = 62.8 μdef for the riding surface; σ_t = − 0.118 MPa with σ_(t, perm) = 0.427 MPa representing the permissible valuefor the base layer and ε_z = 103.8 μdef, ε_(z, perm) = 487.3 μdef for the sub-base layer; which reassures us that the pavementstructure is durable.