Pore-pressure increase is one of the most significant triggering factors for slope failures in many regions around the world, mainly in tropical climates, where residual and colluvium soils are abundant. In order to analyze and understand the mechanisms and conditions leading to such failures, this thesis presents a study of the soils behavior under triaxial tests of pore-pressure increase, that mimic the elevation of piezometric level in slopes. The tests were performed on soil samples of two colluvial and one young residual soils from different slopes in Rio de Janeiro. Additionally, direct shear tests with cut plane and polished surface, and conventional undrained and drained triaxial testing were carried out to obtain the residual shear strength and the critical state line of soils, and illustrate the behavior differences under different stress paths. Internal instrumentation and a miniature pore-pressure transducer at the mid-height of the specimens were used to monitoring local deformations of the specimens and get appropriate porepressure measures. The results showed that under the effect of pore-pressure increase each soil showed different behavior. It is attributed mainly to the degree of weathering and their differing structural features. It was also observed that the stress path followed in the tests have a significant influence on the strength characteristics of the large strain state of soils.