Caracterización experimental del comportamiento hidromecánico de una arcilla compactada

Abstract

The characteristics of the compaction process condition the hydro-mechanical behaviour of soils imposing to them certain structure, a suction and an initial state of preconsolidation. Two of the aspects little studied in these soils are the effects of the anisotropy derived from the compaction process and the connection between the deformations and the humidity changes when they are under changes of suction or tension. In individual, it is to emphasize that in relation to these two aspects there exist until present few experimental results, specially in triaxial conditions.<br/>The primary objective of the Thesis has been to obtain useful guidelines of behaviour experimentally to develop conceptual constitutive models that cover the indicated aspects. For this, the hydro-mechanical behaviour of a statically compacted soil with an open fabric has been analyzed under controlled tension and suction paths having considered the stress history achieved out during the compaction. The secondary target, but necessary to reach the primary target, has been to construct and put to point a suction-controlled triaxial cell, automated. One of the most relevant aspects of the cell is the possibility to measuring sample deformations both local and global form.<br/>The tests have been performed on the one dimensionally compacted Barcelona clay. Characterization of the structure of compacted soil has performed by means of electronic microscopy (ESEM) and mercury intrusion porosimetry (MIP). The test procedures to put to point are described in detail in the text of the Thesis. <br/>In the tests, it has been observed that due to the soil deformation, the changes in the retention curve of the material lead to that an increase of soil water on loading under a low suction (10 kPa). In this loading path with higher suctions a reduction of water has been observed. <br/>The tests have shown that the initial yielding curve of the soil can be displayed as an inclined elliptical form and that during the initial phase of isotropic loading path is observed appreciable shear strain. The axis inclination of the ellipse shows similar features that the inclination of stress paths followed during the compaction in conditions of null lateral deformation. As increasing the applied load or reducing the suction, accumulating irreversible deformations, a progressive tendency towards isotropic behaviour of the soil has been observed. On the other hand, it has been observed that the relations between shear and volumetric plastic strain increment are similar when collapse paths by decrease, suction or increase loading are followed. <br/>The experimental results have been interpreted using as conceptual framework the Barcelona basic model, the model for saturated anisotropic soil of Wheeler et al. (2003) and the hydromechanical model of Vaunat et al. (2000).