The 14th ALERT Olek Zienkiewicz course was held in Aix-en-Provence, France, from April 22nd to April 26th 2024.

It was organized by the research unit RECOVER from Aix-Marseille University, INRAE in relation with the doctoral school 353 “Engineering sciences: Mechanics, Physics, Micro et Nano-electronics”.

Organizers

Antoine Wautier, Nadia Benahmed and Pierre Philippe

Objectives

How to characterize and model the hydro-mechanical behavior of geomaterials from the microscale to the  structure scale?

Program

Detailed content of the course

1- Hydraulic actions on soil: erosion, hydro-mechanical instabilities (P. Philippe, 2h)

General context: flood risk, protective structures, external and internal erosion
Surface erosion: local law(s), erosion lab tests and interpretation models
Example for piping erosion and contact erosion
Hydro-mechanical instabilities: fluidization, gravity collapse

2- Mechanical behavior of granular materials (N. Benahmed, 2h)

General concepts: strain, stress-strain relationship, effective stresse
Experimental characterization of geomaterials: different types of tests, drained/undrained behaviors;
Volumetric strain behavior (contracting/dilatation), triaxial shear strength, relationship with constitutive soil properties
Instability and failure of geomaterials: instability line, characteristic line, critical state (Mohr-Coulomb criterion)
Examples of instability-related disorders

3- Mechanical instabilities and failure in granular materials (A. Wautier, 2h)

Definitions: instability, bifurcation, failure
Granular plasticity: interlocking between elasticity and plasticity, non-associated plasticity, incrementally non-linear plasticity
Failure modes: diffuse or localized failure, material or structural softening
Instability criteria: plastic limit surface, localization criterion, second-order work criterion
Microstructure impacts on granular plasticity and mechanical stability (rattlers, fine or coarse content)

4- Mixing properties in granular media (M. Souzy, 2h)

General concepts: mixing, dispersion, molecular diffusion, stretching laws
Mixing in dry granular media, segregation, rotating drum, fluidized bed, vibrations
Mixing of particle suspensions, interstitial flow, lamellar approach, Diffusive Strip Method, coalescence
Mixing in porous media, experimental characterization of stretching laws, 3D velocity fields in porous medium, anomalous dispersion
Example of particle suspension flow in a constriction: risk of clogging and intermittent flow

5- The Discrete Element Method (DEM): a numerical modeling approach adapted to geomaterials (J. Duriez, 2h)

Presentation of the DEM calculation cycle
Contact laws, particle shape, numerical damping, parallel calculation concepts
DEM as a tool for virtual experiments providing continuum stress and strain quantities
Overview of hydro-mechanical couplings

6- Practical session: Implementation of a 1D minimal DEM code and introduction to YADE  (A. Wautier, 3h)

This session requires that students have a computer (loan possibilities to be discussed with the teacher)  Python (https://www.python.org/) installed, and know how to use classes.
For the YADE part: Ubuntu desktop with sudo apt install permission or any other Operating System with Docker installed.

7- Multi-phase Lattice Boltzmann Method (LBM) and its Application to Partially Saturated Granular Soils (Theory and Practice) (N. Younes, 2h)

Origins, Background, and Theory
Benchmarks (Real-time Tutorial)
Coupling with the Discrete Element Method (DEM) for simulating partially saturated granular assemblies at the Representative Elementary Volume (REV)
Modeling Partially Saturated Granular Assemblies: Investigating various aspects at the REV scale, including suction, capillary stress, and more.

8- Simulating large displacement problems in Continuum Mechanics with the Material Point Method (MPM) and CB-Geo MPM – PyCBG softwares (J. Duriez, 2h30)

Overview of the MPM formulation for solving linear momentum balance equation in continua : capabilities and limitations of MPM
Hands-on activity on MPM simulations with the CB-Geo MPM code and its PyCBG interface
Ubuntu desktop with sudo apt install permission or any other Operating System with Docker installed

9- Safety assessment of civil engineering structures (L. Peyras, 2h)

Introduction to operational safety
Functional analysis
System failure mode analysis: overview of the existing methods (APR, APD, AMDE, AMEC, HAZOP)
System failure scenario analysis: overview of the existing methods (event trees, cause-trees, bow-tie)
System safety assessment: probabilistic, semi-probabilistic, expert
Illustrated examples on civil engineering systems

10- Uncertainty propagation and reliability analysis (C. Carvajal, 2h)

Introduction of uncertainties in mechanical modeling
Random variables and random fields
Mechano-fiabilistic coupling: First-Order Reliability Method, response surfaces, Monte-Carlo simulations

11- Practical session: Mechano-fiabilistic computations for the risk assesment of the rupture of a dam (L. Peyras et C. Carvajal, 2h)

Application of courses 9 and 10 on the real case of a dam

Practical information

The course will be held in Aix-en-Provence (France) from Monday April 22nd to Friday April 26th. The lecture room is located in “Le cube” on Aix-Marseille University campus. The address is 29 Av. Robert Schuman, 13100 Aix-en-Provence.

The room number is 201 located on the second floor. 

Here is a map of the campus.

To reach Aix-en-Provence by train the most convenient is to stop at Aix-en-Provence TGV (note that there is also a train station in Aix-en-Provence city center but accessible only with regional trains) and then take the bus 40 to the city center. Participants coming by plane can land at Marseilles Airport and also reach Aix-en-Provence by bus 40.

To move around in Aix-en-Provence, you can check public transportation here : https://www.aixenbus.fr/fr/

On Friday, we will propose to participants to come to visit the geomechanics and geosynthetics labs at INRAE and then take a tour in the mountain Sainte-Victoire. From Aix-en-Provence, to reach the premises, take bus 13 or bus 110 to Le Tholonet (stop at Ferrageon).

On the Monday evening, a poster session will be organize for the participants to share their research work. A cocktail will be served during the poster session in the spirit of ALERT famous poster session.

There is no registration fee for the course. Lunches and coffee breaks should be included. The participants will need to cover travel, hotel and diner costs.

Contact

For any question, please feel free to contact Antoine Wautier, Nadia Benahmed or Pierre Philippe