Abstract
In this experimental study the influence of fissuring orientation and confinement pressure on the mechanical behaviour of natural clays is investigated. The tested material, the scaly clay from Santa Croce di Magliano (south of Italy), is characterised by an intense network of pre-existing fissures of single orientation. Several plane strain compression tests have been conducted, under different confinement pressures (i.e., from 50 to 600 kPa), on specimens having fissures with vertical, medium and horizontal inclination. Digital Image Correlation has been used to follow the deformation processes of the specimens throughout the tests by measuring incremental shear and volumetric strain maps. The results showed a strong coupling between the total confinement and the fissure inclination, that is controlling both the onset and the development of the patterns of the localisation processes. The new results have been compared with previous ones carried out on the same material without confinement. The comparison shed light on the role of total confinement that becomes particularly relevant from certain levels of pressures and fissuring inclination.
Highlights
Soils outcropping within chain areas have generally experienced long geological histories as a result of tectonism
Here-forth, the influence of both fissuring inclination and confinement pressure on global behaviour and strain localisation phenomena has been investigated. This has been pursued through the analysis of both the global stressstrain response during plane strain compression tests and the evolution of displacement and strain fields throughout the same tests, the latter carried out by means of 2D Digital Image Correlation (DIC)
Plane strain tests with different confinement pressures have been conducted in Lund University (Sweden) on several SCM scaly clay specimens with different fissure inclinations
Summary
Soils outcropping within chain areas have generally experienced long geological histories as a result of tectonism. It is an allochthonous clay, since it was originally deposited hundreds kilometres away from its current location and was subsequently subjected to large displacements during the Apennine orogenesis It follows that its pre-existing fissures can be seen as the current product of the in-situ strain localisations phenomena induced by the large deformations experienced by the clay during its complex and long geological history. Plane strain (biaxial) tests with different confinement pressures have been conducted in Lund University (Sweden) on several SCM scaly clay specimens with different fissure inclinations These new results could shed light into the coupling between the effect of confining pressure and fissure orientation on both the global response and the local patterns of soil behaviour
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