Automated K0 consolidation in stress path cell

Due to the fact that several natural soils have been deposited under zero lateral strain, it is worth to carry out triaxial tests without lateral deformations known as K-0 consolidation. In this case the real K-0 value is not known in advance. In order to measure this value, a LabVIEW software is used to control a Bishop and Wesley stress path cell. The software program can operate three digital pressure-volume controllers that measure and control the volume change and pore water pressure, the radial stress and the axial stress or strain. This paper describes a fully automated K-0 consolidation of the test sample at zero radial strain. Using the horizontal Hall effect local strain transducer, radial deformations can be directly measured on the soil specimen. Therefore radial strain can be monitored continuously during the consolidation process. Steering that the volume change of the soil specimen must always be equal to the vertical deformation keeps the average cross-sectional area constant. This method is applicable only to saturated soils. In this research a constant rate of the axial deformation is applied and by means of a feedback signal from the horizontal local strain transducer the radial stress is controlled in order to keep the radial strain zero. From several triaxial test results, it is found that the LabVIEW program enables to control the stress path cell for investigating the real K-0 value in consolidation.