The Effects of Strain Localization on the Determination of Critical State Seen with Experimental and Numerical Models

Abstract

The paper aims to study the role of strain localization on the results of triaxial test on sand and more particularly on the determination of the Critical State. To this aim, triaxial compression and extension tests have been performed by adopting the tomographic technique and digital image correlation to detect strain localization. Then the tests have been numerically simulated adopting a recent advanced Critical State constitutive model. The simulation, firstly carried out with the classical element test approach, i.e., considering the sample as a single element representative of the soil behaviour, has proven to be unable to capture the soil response under the various loading conditions. Then the analysis has been repeated assuming the triaxial test as a physical model, i.e., introducing the boundary conditions given by the tests and simulating the sample as made of different elements each of different initial porosity, as observed from the tomography. The analysis reveals the importance of strain localization on the test results and points out the limitation of the traditional approach to evaluate the soil properties at large strains.