Impact of water on physical and mechanical properties of calcareous rocks used in engineering structures

The internship will be hosted by CY Cergy Paris Université (CYU) in the “Géosciences et Environnement Cergy” laboratory, the GEC lab. Gec is member of the Institut des Matériaux (i-Mat) federation at CYU.

GEC lab: https://gec.cyu.fr

i-Mat federation: https://cyimat.cyu.fr

Context:

This project is part of the ANR MENHIR project (for “Modélisation mécanique et ENvironnementale pour une approche Holistique et Interdisciplinaire de la Réhabilitation des ouvrages maçonnés ») which objective is to propose reliable tools to evaluate mechanical and environmental performance of existing masonry structures in civil engineering. For this purpose, three structures were selected, two bridges and one retaining wall: the main goal of the present work is to conduct a complete characterization of the constitutive materials for these structures, focusing on petrophysical, microstructural and mechanical properties, and the impact of water on the latter.

Objective:

A thorough rock characterization will be done for each selected target, using the analytical equipment of the GEC laboratory and the microscopy tools of the “Imaging and Analysis” i-Mat platform. More precisely, three studies will be conducted:

• Microstructural study: mineralogical composition, grain size and shape, pore size and shape
• Petrophysical study: density, porosity, pore size distribution through mercury injection, capillarity, permeability, water vapor adsorption
• Mechanical study: static and dynamic elastic moduli, uniaxial compression strength, tensile strength, creep tests, fracture toughness, fracture energy

The mechanical study will be done firstly on dry samples, secondly on “wet” samples with controlled water content. Due to physico-chemical interactions between water and minerals, water is known to induce weakening in porous rocks, resulting in a decrease in elastic moduli and mechanical strength. The damage experienced by the rock samples during mechanical loading will be analyzed through ultrasonic (and possibly electrical) monitoring. The results of the experiments carried out at GEC laboratory will feed numerical models that will be developped by other partners of the project.

We seek a second year master student from

(i) masters in geosciences with significant background in rock mechanics and rock physics,

(ii) masters in applied physics or civil engineering with interest in Earth sciences.

The student must show a strong interest for experimental laboratory work. The Master student will have the possibility to follow a project from the beginning to the end, including sample preparation, physical measurements, microstructural studies and the analysis and interpretation of the obtained data set.