Multi-scale Investigation of Degradation Processes in CementedGranular Materials<\/p>\n\n\n\n
X-ray and Neutron Tomography; double-scale FEMxDEM coupling
Context: Cemented granular materials, ranging from sandstones to grouted sands, are ubiquitous in natural
and engineered environments. The three main micro-mechanical processes governing the degradation of
these highly heterogeneous materials are commonly identified as (i) cement damage, (ii) grain crushing and
(iii) fragment rearrangement. Recently, micro-inspired constitutive models (e.g. [1,2,3]) aim to acknowledge
this connection by including internal variables representing these processes influencing the macroscopic
response of the material. Nonetheless, experimental validation by quantitative characterization of cement
damage processes and its evolution in time and space cannot be fully captured and quantified by X-ray
tomography (CT), currently the most used non-destructive technique in laboratory geomechanics. While X-ray
CT provides useful information on the degradation process, a clear distinction of cement and grain damage
requires the acquisition of complimentary 3D image modalities.
Project Proposal: A novel approach to this problem consists in complementing the use of X-ray imaging with
Neutron tomography. Neutron flux attenuation is sensitive to different chemical species inside a material and
can therefore reveal highly complementary and rich information about the degradation at the cement bridge
sites. The candidate will focus on the design, performance, and analysis of experimental campaigns where
triaxial loading of an artificial sandstone is performed while acquiring X-ray and neutron CT simultaneously.
The rich dataset will enable a comparison of different types of cement, grain surface bonding effect and grain
properties. The candidate will study the relationship between damage distribution and its evolution on the
material response, by using advanced segmentation, correlation and image analysis tools. (Fig.1)
Complementarily to the experimental work, the candidate will be conducting a multi-scale numerical study on
the degradation process of cemented granular materials. This numerical part will be performed within the
framework of a multi-scale approach, combining the discrete element method (DEM), considering the granular
microstructure, and the finite element method (FEM) representing the macro (sample or structural) scale. In
this spirit, a double-scale framework is operational and continuously developed at the 3SR laboratory [4]. The
candidate is expected to learn about the approach and take part in developments pertaining to the current
project. Advances will be made on the following topics: creation of tomography based numerical periodic
microstructures, integration of particle fragmentation, enrichment of contact laws to consider realistic bond
damage, spatial analysis of microstructure evolution. (Fig.2)<\/p>\n\n\n\n
Candidate Skills: The candidate should have a background in civil\/mechanical engineering, material science
or applied mathematics. The ideal candidate has experience and can be autonomous in generating\/analyzing
experimental data (imaging methods, instrumentation, sample preparation \u2026). Good programming skills and
familiarity with scientific languages is an asset (C\/C++, Matlab, Python, Julia, \u2026). Additionally, a strong interest
and experience in using and developing numerical frameworks and\/or constitutive models are highly desirable.
Strong oral and written English communication skills are required.
Location: 3SR laboratory, Universit\u00e9 Grenoble Alpes (UGA), Grenoble, France.
Start date: December 2025
Application: Open August 26th 2025, until a suitable candidate is selected.
Contact: To apply please send an email to Alessandro Tengattini (alessandro.tengattini@3sr-grenoble.fr),
Cyrille Couture (cyrille.couture@3sr-grenoble.fr) and Cino Viggiani (cino.viggiani@3sr-grenoble.fr).<\/p>\n\n\n\n