2020-03-Offer for a Thesis Allowance - Subject: Phase transitions and confined crystallization in inelastic geomaterials

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Offer for a Thesis AllowanceSubject: Phase transitions and confined crystallization in inelastic geomaterials

Abstract

Geomaterials are porous, discrete and heterogeneous media exposed to environmental interactions. These materials host multiple fluids with which they establish physico-chemical feedbacks. During the last decades, major shifts in climate encouraged the study of phase transitions within the pores of soils and rocks, which include salt crystallization, mineral precipitation, freeze/thaw dynamics, and methane hydrate dissociation, among others. Phase transitions are a key source of weathering, as they cause unprecedented alterations in the strength and deformation properties of natural deposits. The overarching objective of this PhD research is to formulate and validate a computational multiscale and multiphysics model for the simulation of geomaterials under cycles of freezing and thawing. The modeling approach will be pursued within the framework of the Lattice Discrete Particle Model (LDPM) with multiphysical constitutive equations formulated in the contest of damage-plasticity. The formulated model will be calibrated and validated on the basis of experimental data gathered from the literature and from tests performed during this project.

Keywords: fracture, rocks, scratch testing, scale effects

 

PhD project

This PhD project is part of the work programme of the international hub “Newpores”, co-sponsored by the laboratoire des fluides complexes et leurs reservoirs (UMR 5150) at E2S UPPA and Northwestern University (Center for sustainable engineering of infrastructures and geological materials.).
Newpores is an international hub gathering over 15 scientists from France, Spain, Belgium and USA, dedicated to the mechanics and physics of porous materials.

 

Missions - principal activities

Geomaterials are porous, discrete and heterogeneous media exposed to environmental interactions. These materials host multiple fluids with which they establish physico-chemical feedbacks. During the last decades, major shifts in climate and the continued exploration of remote environments encouraged the study of phase transitions within the pores of soils and rocks, which include salt crystallization, mineral precipitation, freeze/thaw dynamics, and methane hydrate dissociation, among others. Phase transitions are a key source of weathering, as they cause unprecedented alterations in the strength and deformation properties of natural deposits. Major challenges for the future generations are especially in the context of arctic regions, which are warming faster than everywhere else on Earth. In particular, scarcity of data and lack of scientifically sound predictive models make it very challenging to predict future scenarios. This opens the possibility of unprecedented risks for natural settings, as well as opportunities for rethinking the management and design of modern infrastructure.

This project is rooted in this context and aims to deepen our understanding of the multi-scale, multi-physical behavior of fluid-infiltrated porous geomaterials subjected to alternating cycles of freezing and melting. The project aims to address low-temperature processes starting from the micro-scale, where pore-size effects control the dynamics of liquid–solid transitions and the pressure jump across phases. We aim to upscale these processes at the level of porous continua, where the existence of coexisting phases affects the stresses acting on the solid matrix, as well as the very own constitution of the matrix. Finally, we aim to tackle the mechanics of failure in materials undergoing phase transitions, thus rethinking the methods currently used to assess natural risks and infrastructure deterioration for systems subjected to temperature-induced phase transitions. Research in this area can lead to numerous benefits, including the increase of the durability of materials subjected to frost action, with consequent major reductions in maintenance and repair costs, as well as the prevention of natural hazards and loss of lives in permafrost regions, i.e. some of those most heavily impacted by projected climate changes.

The overarching objective of this PhD research is to formulate and validate a computational multiscale and multiphysics model for the simulation of geomaterials under cycles of freezing and thawing. The modeling approach will be pursued within the framework of the Lattice Discrete Particle Model (LDPM) with multiphysical constitutive equations formulated in the contest of damage-plasticity. The formulated model will be calibrated and validated on the basis of experimental data gathered from the literature and from tests performed during this project.

The project duration is 4 years with 2 years residency requirement at both places. The candidate is expected to earn a Ph.D. from both institutions at the end of the project.

 

Working conditions

Hosting laboratories: Laboratoire des fluides complexes et leurs réservoirs (UMR 5150, https://lfc.univ-pau.fr/en/scientific-activities/focuses-of-research/geomechanics-of-porous-media.html) in association with the Dept. of Civil and Env. Engrg. of Northwestern University, Evanston IL, USA

Localisation: Université de Pau et des Pays de l’Adour, Anglet Campus - 2 years, and Northwestern University (USA) – 2 years

PhD supervisor: Prof. Gilles Pijaudier-Cabot   (gilles.pijaudier-cabot @ univ-pau.fr)UPPA (Anglet, France) 
PhD co-supervisor: Prof. Gianluca Cusatis  (g-cusatis @ northwestern.edu)Northwestern University (Evanston, IL, USA)
In Collaboration with: Prof. Giuseppe Buscarnera   (g-buscarnera @ northwestern.edu)Northwestern University (Evanston, IL, USA)

Starting date: September 2020

Length: 4 years – with 2 degrees from UPPA and Northwestern University

Employer: UPPA, doctoral school ED 211 Doctoral School of Exact Sciences and their Applications, and Northwestern University (USA)

Gross monthly salary: 1878 € during the two years at UPPA (UPPA doctoral contract, according to E2S UPPA project) & PhD fellowship at Northwestern University

 

Required skills and competences - Who can apply ?

The applicants should have a MSc-degree focused either on structural engineering or on rock mechanics.
Inclination towards computational modelling and programming will be highly appreciated.

The candidate should have a strong predilection for laboratory work.
He/She is rigorous, highly motivated, with the capacity to work autonomously.
Team working abilities are highly appreciated.
Good knowledge in English and good writing skills are required.

 

Application - Evaluation criteria

Application files will be evaluated based on the following criteria:

  • Candidate's motivation, scientific maturity and curiosity
  • Academic results : grades and ranking in Licence/undergraduate, M1 and M2
  • English language proficiency
  • Oral and written communication skills
  • Candidate’s ability to present her/his work and results
  • Professional experience (e.g. internships in laboratory or other, any research work previously carried out, reports, publications ...)

 

Selection

Selection process steps (French part):

  • Establishment of the selection comittee.
  •  Evaluation of the applicants cv’s
  • Interview with the selected candidates and ranking.

Selection process steps (USA part):

During the PhD at Northwestern University, students will be enrolled within the Mechanics, Materials and Structures (MMS) programme. Northwestern’s policy is to accept students through a competitive selection process upon reception of an official application.
For information on this application process, perspective students are encouraged to contact  Ms. Melissa Koelling, Academic Coordinator (mkoelling @ northwestern.edu)


Application file composition and submission deadline

To apply, please send an email to  Prof. Gilles Pijaudier-Cabot (gilles.pijaudier-cabot @ univ-pau.fr) with [Newpores - PhD offer] as its subject and the following documents attached:

  • CV
  • Cover letter detailing candidate's motivations
  • Copy of your diplomas and academic records (marks and ranking)
  • Letters of recommendation (if any)
  • Contact details for 2 referees

 

Submission deadline : May 15th, 2020