Synchrotron 4D X-Ray Computed Tomography of a Porous Limestone: Influence of Porosity on Deformation Mechanisms at Multiple Scales

This study investigates the relationship between deformation mechanisms and heterogeneity of porosity of a porous carbonate rock across several scales. The Saint Maximin limestone (SML), characterized by centimeter-scale alternations of dense and porous zones, serves as a model rock to examine the evolution of deformation modes. Cylindrical samples of 8 mm in diameter, extracted from both the dense and porous zones of the SML, were tested in axisymmetric triaxial conditions with in situ synchrotron imaging. High-resolution 3D strain fields and porosity maps were derived from synchrotron images to assess local-scale correlations. The results demonstrate that initial porosity exerts a primary control on strain patterns, spanning from the microscale to the centimeter scale. Under brittle conditions, deformation localizes into bands, predominantly accommodated within the more porous regions, while the denser zones remain largely unaffected. At intermediate confining pressures, heterogeneity induces a transitional behavior where diffuse and localized deformation coexist. In ductile conditions, multiple small compactant bands progressively saturate the sample, leading to porosity homogenization.