Swelling-shrinkage properties of compacted Karal soils from North and Far North Cameroon: a physicochemical and geotechnical approach

Abstract

Karal soils mainly composed of swelling clays are considered as one of the main causes of degradation in civil engineering structures in Cameroon. Thus, a better knowledge on Karal-type soil behavior is required to adapt soil treatment for road construction and foundation dimensioning. The physicochemical, mineralogical and geotechnical characterization of ten soils collected in North and Far North Cameroon allowed to classify Karal among plastic soils. As expected, the optimum water contents and maximum dry densities of dynamically compacted Karal reflected the particle size distribution and the mineralogical soil composition with various amounts of swelling clay (montmorillonite) and quartz associated to sand and silt fractions. Then the swelling/shrinkage properties of compacted specimens evaluated by free swelling test and volume shrinkage test were correlated to soil characteristics to propose a suitable classification for Karal-type soils. Not only swelling but also shrinkage properties were assessed and combined to define a new parameter called the total amplitude of swelling and shrinkage deformation, allowing the exclusion of the soil initial water content when evaluating soil deformation. After comparison of usual indirect methods to classify swelling soils, a predictive method of clay-rich soils deformation under moisture variation for Karal was proposed and discussed.