arXiv subjects

Patrick Aimedieu

Publications and source records attributed to Patrick Aimedieu.

3 recordsLinked to original sources

arXiv2026

Morphology-resolved stress contributions in sheared wet granular materials

Three-dimensional X-ray microtomography, coupled to rheometric measurements, enables a morphology-resolved reconstruction of capillary stresses at the grain scale in unsaturated wet granular materials. Liquid domains are automatically classified into capillary bridges, dimers, trimers, and larger clusters, and their spatial organization is tracked as a function of shear deformation and liquid content. We show that shear localization governs the redistribution of the liquid phase: capillary bridges remain uniformly distributed throughout the sample, while higher-order morphologies accumulate preferentially near the lower boundary of the shear-zone through a shear-driven coalescence mechanism. Despite this spatial localization, simple two-grain bridges generate the dominant contribution to the isotropic capillary pressure, accounting for nearly 85\% of the total at liquid-to-solid volume ratio $\epsilon = 0.05$, whereas more complex liquid clusters contribute only weakly to the overall cohesion. Incorporating the morphology-resolved capillary pressure into an effective-stress framework qualitatively reproduces the macroscopic friction coefficient across the full range of investigated liquid contents, without adjustable parameters. These results establish a predictive micro--macro link between liquid morphology and the rheology of wet granular materials.

cond-mat.soft↗

arXiv2024

X-Ray microtomography of mercury intruded compacted clay: An insight into the geometry of macropores

Soil properties, such as wetting collapse behavior and permeability, are strongly correlated to the soil microstructure. To date, several techniques including mercury intrusion porosimetry (MIP), can be used to characterize the microstructure of soil, but all techniques have their own limitations. In this study, the features of mercury that penetrated and has been entrapped in the pore network of the specimens through MIP testing were investigated by X-Ray microtomography (X-$\mu$CT), in order to give an insight into the geometry of macropores and possible ink-bottle geometry. Two conditions of water content and density were selected for the compacted Maryland clay. The distribution and geometry features of mercury entrapped in the microstructure after MIP were characterized and pore size distributions were also reconstructed. The results suggest that, for the two conditions studied in this paper, macropores were evenly distributed within the specimens, and most of them with a non-spherical shape, and with aspect ratio (ratio between the maximum and minimum thickness along a given segment) smaller than three. Different dominant entrance pore size of macropore was obtained from MIP and X-$\mu$CT, due to the specific experimental protocol used in tests and the effect of ink-bottle geometry. Only the large pore bodies with high aspect ratio were imaged in X-$\mu$CT, due to the extrusion of mercury during the process of depressurization and subsequent sample preparation for X- $\mu$CT. But entire pore space was accessible in MIP. The difference in dominant entrance pore size was more significant for specimens with lower void ratio due to a more pronounced aspect ratio.

cond-mat.mtrl-sci↗

arXiv2019

Stability criterion for fresh cement foams

We prepare and study cement foam samples with well-controlled structure, i.e. containing monodisperse bubbles. We observe that the foam structure often changes before cement setting and identify ripening as the major destabilization mechanism at stake. Drainage plays only a minor role in cement foam destabilization except when bubble size is large. Then we show that a single stability criterion can be defined, for a large range of cement foams with different formulations. This criterion involves the bubble radius and the yield stress of the cement paste such as confined by and between the bubbles, at a given characteristic time after sample preparation.

cond-mat.soft↗