Investigation Expérimentale de l’endommagement des grains sous fortes contraintes : évolution de la microstructure

Abstract

This research focuses on the fundamental understanding of permeability and its relationship with various physical parameters due to its importance in different contexts, such as the field of petroleum engineering, the design of drainage systems, and the construction of earth dams. A comprehensive study was conducted on ten types of sands, leading to the development of an innovative experimental correlation between the permeability of a granular material, its average diameter, and its density index. This correlation provides an efficient method for evaluating sand permeability based on its physical characteristics, thus avoiding the need for lengthy experimental procedures. The research also explores two major aspects. Firstly, it introduces the development of an analytical model based on the van Genuchten model to predict the water retention curve of granular materials, accompanied by an in-depth study of influential parameters. Notably, the model relies on a singular criterion in soil selection: the physical property of the particle size distribution curve, allowing the determination of Dg50 and Cu values. This model offers a precise description of the water retention curve and enables the estimation of the pore size distribution without the necessity for experimental tests. The use of the proposed model allowed predicting the water retention curves of granular soil for any value of the density index. The results confirm that the uniformity of particle size distribution curves corresponds to a satisfactory uniformity of the pore size distribution. Additionally, the observation of an increase in suction with an increase in density index aligns with experimental data, highlighting distinctive properties of unsaturated soils. Subsequently, the study delves into the evolution of the microstructure of granular materials under various physical and mechanical conditions. Water retention curves are transformed into pore size distribution curves, allowing for an in-depth analysis of microstructural changes under high constraints. In summary, this work provides a significant contribution by offering practical correlations for evaluating the permeability of granular materials and developing a robust analytical model to predict the water retention curve. Furthermore, it thoroughly explores the evolution of microstructure under different conditions, providing crucial insights into the understanding of granular materials subjected to high constraints.