Evaluation of Heterogeneities in Reconstituted Samples using X-Ray tomography

In the process of characterization and modeling of the mechanical behavior of geomaterials assumptions are adopted related to the theory of continuous medium, such as homogeneity and isotropy condition derived from the stress-strain response. Thus the development of element tests on undisturbed samples or reconstituted in laboratory the actual evaluation of discretization and heterogeneity of the environment are not considered, and their impact on the response of shear strength, this fact extends to the numerical implementation of different constitutive models through the application of finite element methods and discrete elements. Among the methods for the reconstitution of sand samples in a laboratory we have compaction, pluviation and moist tamping to determine the density levels achieved in the manufacture of loose or dense homogeneous samples. These samples are used in stregth tests such as the triaxial resistance without taking into account the definition of an indicator to establish the real state of heterogeneity of the same. The progress of prospecting techniques in medicine such as X-ray computed tomography has transcended to other fields such as the quality assessment of materials engineering. A proposal for assessing the condition of heterogeneity of sand samples considering the main building techniques shown in this paper, based on the development of tomographic images and the subsequent treatment of the Hounsfield [HU] information density readings with the initial application of image segmentation techniques that allows to obtain baseline data points and the subsequent statistical analysis of variability considering different volumetric groupings. So a reconstitution evaluation measure is reached of soil samples that could be generalized to the analysis of undisturbed samples, allowing analysis of relationship structure - mechanical response characterization tests and shear strength. The results of this study show a high influence of the boundary conditions in the heterogeneous spatial distribution of the density in reconstituted samples with the methods considered, also allows to think about the use of this methodology as a tool for reviewing and adjusting of such methods and its application to the study of undisturbed samples.

This heterogeneity study could be incorporated into the constitutive modeling through the definition of characteristic parameters of the model and a coherent analysis of inherent and induced fabric tensors.