Laboratoire Navier

Predicting the evolving microstructure of hydrating cement is essential for understanding and modeling its mechanical property development. Physics-based continuum approaches offer a rigorous framework for capturing the thermodynamics of dissolution and precipitation processes at the microstructural scale. In this work, we present an adapted Phase-Field (PF) model for cement hydration that resolves key physical inconsistencies in existing PF formulations by introducing a revised free-energy potential and distinct equilibrium constants for clinker dissolution and hydrate precipitation. The resulting PF framework reproduces microstructural evolution, yielding realistic porosity levels and continuous phase boundaries in close agreement with experimental observations. The predicted hydrated microstructures are subsequently used in a computational homogenization scheme to evaluate the elastic response of the material. The PF-derived mechanical properties show good agreement with experimental trends, supporting the ability of the proposed framework to consistently link hydration chemistry, microstructure formation, and the resulting mechanical response. • A PF model predicts the microstructure evolution during the alite hydration. • The estimation of the sample behavior is based on the predicted microstructures. • Predicted microstructures and elastic moduli show agreement with the literature.

Abstract During an earthquake, slip occurs in a localized shear zone that features a heavily granulated fault core that can be characterized as a shear band. We study the formation of this fault core in a granular rock such as sandstone by developing a model of crushable granular media within the framework of Breakage Mechanics. This model accounts for the evolution of the grain size distribution, while also accounting for the co‐evolution of the solid fraction. An enrichment with the Cosserat continuum allows for the model to predict finite‐width shear bands. The model is then calibrated against experimental data taken from tests on Bentheim sandstone, and a parametric study of the mechanical parameters is conducted using linear stability analysis. We find that for deeply‐buried rocks the shear bands have a compactive component, and the initial value of the solid fraction does not play a strong role in the initial band thickness, but can influence the rate of delocalization of the band. Post‐localization behavior is studied with the finite element method, which shows the formation of zones of dilation outside the band in addition to the compaction within the band. Using a modified Kozeny–Carman permeability law, it is shown that within the band the permeability reduces by several orders of magnitude, but can increase outside the band. Our results highlight the importance of modeling grain size and solid fraction evolution as they exert a controlling influence on hydromechanical properties that play an important role in fault formation and seismic slip.

Le changement climatique perturbe les écosystèmes, affecte les phénomènes météorologiques et le cycle hydrologique. En zone urbaine, ses impacts sont plus ressentis en raison de l'imperméabilisation des sols, la faible végétalisation et la pollution. Les arbres en ville offrent de multiples services écosystémiques et se présentent comme une solution possible pour atténuer ces effets. Les arbres interagissent notamment avec le cycle hydrologique et le climat urbain. Afin d'optimiser ces avantages, il est proposé de quantifier et de qualifier le rôle des arbres dans l'espace urbain du point de vue hydrologique et écophysiologique en travaillant à l'échelle pilote sur un système bio filtrant existant, appelé « l'arbre de pluie ». L'objectif de la thèse est l'évaluation de la performance hydrologiques des arbres d'alignement recevant les eaux pluviales adjacentes en vue de leur gestion en maintenant voir améliorant leur fonctionnement eco-physiologique.

Spectral geometry is a mathematical field that links geometrical properties to eigenvalues of differential operators on surfaces. Although it is a well-established tool in geometry processing and has been used in many contexts, the structural engineering and architectural geometry communities have not yet adopted this framework for shape modeling. This paper aims to explore spectral methods for applications in architectural geometries. A novel methodology for generating anisotropic Laplacian operators based on regions of interest defined by the user is proposed. The potential of spectral methods in structural design is illustrated through design problems expressed on meshes and graphs. • Spectral geometry is proposed as a generic modeling framework for free-form structures. • Feature-aligned anisotropic Laplacian operator is introduced. • Linear and affine constraints are handled.

A soil–bentonite vertical cutoff wall is commonly employed as an effective engineered barrier in contaminated sites to prevent the spread of chemical pollutants. Over time, the soil–bentonite backfills experience suction changes due to alternating rainfall and evaporation processes, as well as fluctuations in water levels, leading to a decrease in the inhibition capability and a settlement in the soil structure. To clarify this point, water retention tests and microscopic tests were conducted on a type of soil–bentonite backfill which was composed of river sand and a low content of bentonite (5%). Experimental results demonstrated that the water retention curve exhibited a typical anti-S-shaped pattern. By considering the air entry value ψAEV and the residual suction ψr as the dividing boundaries, three distinct zones could be closely identified from the water retention curve. The water loss and soil shrinkage of sand–bentonite backfills displayed similar development trends, with significant changes at the low-suction zone (ψAEV <s < ψr) and less noticeable changes at the high-suction zone (s > ψr). The pore structure of the backfill evolved from a single-porosity to a double-porosity structure with the increase of suction, and finally returned to a single-porosity structure while approaching to the dried state. This transformation in the pore structure was influenced by an aggregation of bentonite layers and the exposed pores between sand particles. A calculation method on the basis of water retention mechanisms was developed to quantitatively analyze the micropore evolution, and its accuracy was validated through a comparison with experimental data.

Abstract 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.

Life cycle assessment (LCA) can be used to evaluate the environmental impacts of urban projects, but requires a huge amount of data. Geodata currently available can be used as soon as the design phase. Here, we explore the potential contribution of existing geodata to improve the accuracy of building energy modeling (BEM) carried out during the LCA of urban projects. Hence, we have built a model to assess the influence of solar masks on building energy needs and indoor thermal comfort. We use this model to assess the benefits of considering these masks. We then test the use of existing IGN geodata to take into account solar masks formed either by adjacent buildings (BD TOPO), or by buildings and vegetation (LIDAR HD). After the model is validated, we use it on two existing buildings to compare the results of simulations with and without masks. These initial tests confirm the interest of using existing geodatabases. They also encourage us to develop guidelines for BEM and LCA practitioners, and to explore the use of geodata to specify other parameters useful for BEM.L'analyse de cycle de vie (ACV) peut être utilisée pour évaluer les impacts environnementaux d'un projet urbain, mais nécessite un très grand nombre de données. Or, de nombreuses géodonnées aujourd'hui disponibles sont mobilisables dès la phase de conception. Nous explorons ici l'apport possible de référentiels géonumériques existants à l'amélioration de la précision des simulations thermiques dynamiques (STD) réalisées lors d'ACV de projets urbains. Pour cela, nous avons construit un modèle permettant d'évaluer l'influence des masques solaires sur les besoins énergétiques de bâtiments et sur le confort thermique à l'intérieur de ces derniers. Nous utilisons ce modèle pour évaluer l'intérêt de prendre en compte ces masques. Nous testons ensuite l'utilisation de référentiels IGN existants afin de produire des données sur les masques solaires formés soit par les bâtiments seuls (BD TOPO), soit par les bâtiments et la végétation (LIDAR HD). Après avoir validé notre modèle, nous l'utilisons sur deux bâtiments déjà construits, pour comparer les résultats des simulations sans masque et avec les masques issus des référentiels. Ces premiers tests confirment l'intérêt d'utiliser les référentiels existants. Ils nous invitent également à poursuivre vers la formalisation de recommandations pour les développeurs d'outils STD et ACV, et à explorer l'utilisation de géodonnées pour préciser d'autres paramètres utiles aux STD.