Performance of a Cubical Triaxial Apparatus for Testing Saturated and Unsaturated Soils

This paper deals with the performance of a stress and suction-controlled cubical triaxial device developed to test 6-cm cubical soil specimens in saturated and unsaturated conditions. In saturated tests, saturation is achieved by back-pressure while matric suction during unsaturated tests is imposed to the specimen assuming valid the axis-translation technique. The paper describes details of the new device, the testing methodology, as well as presents a series of drained conventional triaxial compression tests on a young residual soil from gneiss performed with the new equipment. The developed apparatus works properly and is adequate to perform tests at different stress-paths that can be helpful to obtain soil parameters needed in the development or improvement of constitutive models for soils. Test results compare well with results from conventional triaxial tests and have showed that suction increased the initial stiffness and the shear strength of the soil, which is commanded by an increase of the cohesion intercept, since the friction angle remained approximately constant.