OSUG - Terre Univers Environnement

Miriam Patricia ORTEGA RAMíREZ

Sources et flux de matières / soutenance en 2018

22 février 2017 ( maj : 18 mai 2018 )

Analysis of soils structural and transfer properties using pore scale imaging and numerical modeling

directeur de thèse : Laurent Oxarango

Date de début de thèse : septembre 2015

The understanding of the behavior of a fluid through the soil, plays an important role in environmental and engineering process such as : the application of contaminants or agrochemicals in the soil, the underground storage of contaminants or waste disposal, soil remediation, soil improvement based on microbiological activity. In recent years, numerous models have been developed attempting to simulate this behavior. However, as they may be considered as a tool to improve decisions on environmental regulatory issue, we must improve these models in the sense that they must be sufficiently tested and contain a comprehensive understanding of the soil. Recent advance in X-ray micro-CT (Computed Tomography) offers a major improvement concerning the analysis of pore scale phenomenon occurring in soils during water flow and solute transport. My PhD project aims at developing new methodologies to investigate soil properties and transfer processes behavior :

In a first phase I chose the software GeoDict to provide me the velocity field for a given 3D image obtained via a CT scan of a sand sample. Using this software, and software developed by the PROTINUS team, an exhaustive characterization of the geometrical and flux properties was done. This phase included an internship at UNAM (México) working with Dr. Alfonso Gastelum and Dra. Blanca Prado, collaborating members of the PROTINUS project.

In a second phase the specific case of bacteria transport in the pore volume will be addressed. I will use the local stationary velocity fields to compute the Lagrangian transport. Results from this model will be compared with a parallel research (done by a Posdoc researcher) on bacteria transport in the same sand with a experimental approach.

As a third phase, the direct numerical simulation of solute reactive transport will be addressed. A numerical model based on the Volume of Fluid approach will be modified to deal with the specific heterogeneous boundary condition associated with the bacteria collection on the grain surfaces.

This project aims at gathering existing numerical tools and creating new ones in order to develop a coherent software package suitable for comparing various type of soils. In the preliminary phase, the existing data-base of x-ray CT images of soils obtained at LTHE from 2015 will be used. These first samples will progressively be included in a data-base (created in the project H2020 PROTINUS) including samples studied at the micro-CT facility at Grenoble University, UNAM (México City, México) and at Kumamoto University (Japan).

This PhD program will also have a significant interaction with the FUI project BOREAL (2014-2018). The second part of the project, focusing on transfer processes, my research will be fed by experimental campaigns of micro-CT analysis coupled with classical column transfer experiments. A strong interaction is planed between the present project and this experimental project that started in November 2014. This interaction will allow me and the experimentalists to develop a Theory/Experiment approach which is very relevant for studies in the field of environmental science.