Suction effects on the tensile strength and unconfined compression of unsaturated soils

The soil-water characteristic curve is an important relation of unsaturated soils, that expresses the variation of the amount of water retained in the soil as a function of its suction. In these soils, drying or wetting can have a great influence on their resistance parameters. This work presents and discusses the effects of increased suction on the tensile strength and unconfined compression of unsaturated soils. Suction was evaluated using the filter paper and the dew point technique, while the resistance parameters were obtained through the “Brazilian Test” and uniaxial compression. Three different soils from Rio de Janeiro were studied: two young residual soils, in which the influence of the soil structure was also verified through tests on undisturbed and reconstituted samples, and a colluvial soil. The results allowed to conclude that the increase of suction, in a first moment, generates an increase in the resistance parameters of these soils. With the continuation of the drying process, the mechanical behaviour of the soils varied, being able to maintain the resistance or showing a drop related to high suction values