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EURAXESS

MSCA-COFUND-CLEAR-Doc-PhD Position #CD22-18: Behavior of frozen soils from micro to macro : experiments and numerical modelling

13/10/2022

Job Information

Organisation/Company
Université Gustave Eiffel
Department
NAVIER
Research Field
Physics
Geosciences
Engineering
Engineering » Mechanical engineering
Researcher Profile
First Stage Researcher (R1)
Country
France
Application Deadline
Type of Contract
Temporary
Job Status
Full-time
Hours Per Week
35
Is the job funded through the EU Research Framework Programme?
H2020 / Marie Skłodowska-Curie Actions COFUND
Marie Curie Grant Agreement Number
101034248
Is the Job related to staff position within a Research Infrastructure?
No

Offer Description

Naturally frozen soils (permafrost and seasonally frozen soils) cover around 20% of the land surface on Earth. Over the past decades, these areas have been subjected to warming, which affects the equilibrium conditions of frozen soils, causing major ground perturbations compared to other regions. These changes pose a threat in terms of natural hazards affecting the infrastructure of cities in the periglacial, high altitude environment around the globe (e.g. warming induced progressive failure of frozen slopes) or in high latitude regions such as areas of Canada, Alaska, Russia or China, to name but a few.

Artificially frozen soils experience similar processes. Their applications include enabling works for underground construction, stabilizing the ground to prevent thawing in permafrost, or increasing the thermal storage capacity of the ground.

Increasing temperatures lead to the partial melting of ice contained in soils and cause the degradation of their mechanical properties and bearing capacity. Such degradation would jeopardize the stability of constructions located in cold regions.

This project aims at investigating the behavior of frozen soils resulting from the loss of ice content. Experimental approaches will be conducted at different scale levels: the particle level, the continuum level, and the real case level. Constitutive equations will be developed and implemented into a FEM code to model real cases and provide a tool for risk assessment.

Despite their prevalence and growing importance, to date, most approaches to explain frozen soil behavior have focussed on phenomenological models that cover its macroscopic behavior. However, the processes underpinning the microstructural changes are not fully explained yet and thus are not included in predictive models. Hence, we hypothesize that an approach considering ice-particle interaction at the solid particle scale can help to provide better and novel tools to understand and predict the behavior of frozen soils. Such a revolution has been recently happening for cemented soils, where the cementation agent is not ice, but mineral precipitation or cohesive material that bonds particles together.

High-resolution X-ray Computed Tomography or micro-Computed Tomography (XRμCT) is frequently used as a non-destructive 3D imaging and analysis technique for the investigation of internal structures of a large variety of objects, including geomaterials. However, it is rarely used to investigate the pore-scale morphology of frozen soil. In addition, in situ XRμCT combined with volumetric digital image correlation has been recently shown appropriate to investigate the deformation and the failure of soil under mechanical loading. However, this technique has never been used to investigate frozen soils.

Constitutive modeling of frozen soils is mainly based on continuum mechanical approaches, which utilize conventional elastoplastic and/or damage frameworks, extended with specific components to account for ice content, cryo-suction, and thermal effects. These components include the soil freezing characteristic curve, hardening functions, non-linear elasticity, etc. Several authors proposed (macroscopic) constitutive models considering creep and rate effects. These constitutive models typically require the calibration of many parameters, some of them sometimes having an unclear physical meaning. The number of parameters demands numerous laboratory tests, which form the basis for systematic calibration. To overcome these challenges, one can recourse to simpler physics occurring at a smaller scale, the scale of the material’s microstructure, and upscale this behavior to the macroscale. This allows considering established physical laws, with fewer uncertainties and fewer parameters. Micro-macro upscaling approaches or microstructure-enriched models have also been proposed in the literature to benefit from the knowledge of soil microstructure and deduce the behavior at the macroscale. A general shortcoming of these approaches is related to the assumption of ideal microstructures (matrix-inclusion or particles cemented at their contacts, etc.) or simple micromechanical laws describing the small-scale behavior.

Accounting for realistic microstructures and complex micromechanical behavior can be tackled by using numerical homogenization including the Fast-Fourier-Transform homogenization technique.

The project will use the latest advanced imaging technologies (e.g. XRμCT) to provide a comprehensive dataset of frozen soils under different temperature and loading regimes at the particle level. The results will be compared to the element testing size carried out in a freezing chamber.

The new database of observed behavior will be used to develop and validate novel constitutive relationships. These will be used in boundary value problems which will be solved in finite element models covering multi-scale and poromechanical approaches. The final step towards macro-scale will be taken using these newly developed techniques to calibrate them against real case studies at two levels, one in a controlled physical model in the laboratory and two real case studies: Dawson City landslide (Yukon, Canada), and the artificially frozen ground campaign carried out in Berlin during the construction of the underground works at the famous Unter der Linden street.

The project will provide a unique and novel database and insights from the observed behavior with an unprecedented level of detail as well as novel numerical approaches to frozen soils, never attempted to date.

Requirements

Research Field
Physics
Education Level
Bachelor Degree or equivalent
Skills/Qualifications
  • At the time of the deadline, applicants must be in possession or finalizing their Master’s degree or equivalent/postgraduate degree
  • At the time of recruitment, applicants must be in possession of their Master’s degree or equivalent/postgraduate degree which would formally entitle to embark on a doctorate
Languages
ENGLISH
Level
Excellent
Languages
FRENCH
Level
Good

Additional Information

Benefits
  • High-quality doctoral training rewarded by a PhD degree, delivered by Université Gustave Eiffel
  • Access to cutting-edge infrastructures for research & innovation
  • Appointment for a period of 36 months based on a salary of 2 700 € (gross salary per month)
  • Job contract under the French labour legislation in force, respecting health and safety, and social security: 35 hours per week contract, 25 days of annual leave per year
  • International mobility will be mandatory
  • An international environment supported by the adherence to the European Charter & Code
  • Access to dedicated CLEAR-Doc trainings with a strong interdisciplinary focus, together with a Career development Plan
Eligibility criteria
  • At the time of the deadline, applicants must be in possession or finalizing their Master’s degree or equivalent/postgraduate degree
  • At the time of recruitment, applicants must be in possession of their Master’s degree or equivalent/postgraduate degree which would formally entitle to embark on a doctorate
  • At the time of the deadline, applicants must be in the first four years (full-time equivalent research experience) of their research career (career breaks excluded) and not yet been awarded a doctoral degree. Career breaks refer to periods of time where the candidate was not active in research, regardless of his/her employment status (sick leave, maternity leave etc). Short stays such as holidays and/or compulsory national service are not taken into account
  • At the time of the deadline, applicants must fulfil the transnational mobility rule: incoming applicants must not have resided or carried out their main activity (work, studies, etc.) in France for more than 12 months in the 3 previous years.
  • One application per call per year is allowed
  • Applicants must be available full-time to start the programme on schedule (November 1st 2023)
  • Application rules are enforced by the French doctoral system which specifies a standard duration of 3 years for a full-time PhD together with the MSCA standards and the OTM-R European rules as follows
  • Citizens of any nationality may apply to the programme
  • There is no age limit
Selection process

Please refer to the Guide for Applicants available on the CLEAR-Doc website: https://clear-doc.univ-gustave-eiffel.fr/how-to-apply/useful-documents/

Additional comments
  • The first step before applying is contacting the PhD supervisor. You will not be able to apply without an acceptation letter from the PhD supervisor
  • International mobility planned : ESR will work in RWTH Aachen University (with prof. Raul Fuentes) to work on the numerical simulation of the artificially frozen ground campaign carried out in Berlin during the construction of the underground works at the Unter der Linden street
  • Please contact the PhD supervisor for any additional detail on job offer
  • There are no restrictions concerning the age, gender or nationality of the candidates. Applicants with career breaks or variations in the chronological sequence of their career, with mobility experience or with interdisciplinary background or private sector experience are welcome to apply
  • Support service is available during every step of the application process by email: clear-doc@univ-eiffel.fr
  • Web site for additional job details https://clear-doc.univ-gustave-eiffel.fr/
Website for additional job details

Work Location(s)

Number of offers available
1
Company/Institute
Université Gustave Eiffel
Country
France
City
Marne-La-Vallée
Postal Code
77454
Street
5, Boulevard Descartes
Geofield

Contact

City
Marne-La-Vallée
Website
Street
5, Boulevard Descartes
Postal Code
77454
E-Mail
patrick.dangla@univ-eiffel.fr