Session 1 “Upscaling in Geotechnical Engineering”  – 30^th September 2019

(session in honor of the 70th Anniversary of Roberto Nova),

Coordinators:

Claudio di Prisco (claudio.diprisco@polimi.it) and Cristina Jommi (cristina.jommi@polimi.it) (Politecnico di Milano, Italy), Claudio Tamagnini (Università di Perugia, Italy, claudio.tamagnini@unipg.it)

 
Objectives:

The session celebrates the 70th Anniversary of Roberto Nova, one of the founders of ALERT Geomaterials and a pioneer in several branches of theoretical modeling of the mechanical behavior of geomaterials and geotechnical structures.

The aim of the workshop is to present some of the most recent developments in geotechnical modelling, with particular emphasis on upscaling procedures to obtain fundamental insight on both the behavior of materials at the macroscale and of geotechnical systems at the megascale.

The session will include (i) constitutive modelling of the hydro-chemo mechanical behavior of granular bonded/structured/cemented soils, (ii) stability conditions for geomaterials and controllability theory, from localised to diffuse mode of failures, (iii) discrete element model analyses, and (iv) soil-structure interaction problems including macro-element theory.

ALERT Workshop session 2 – 1^st October 2019:

The mechanics of root-soil systems: from microscopic to macroscopic approaches

Coordinators:

Evelyne Kolb (PMMH & Sorbonne Université, evelyne.kolb@upmc.fr), Luc Sibille (3SR & Université Grenoble Alpes, luc.sibille@3sr-grenoble.fr)

Outline:

The interactions between plant root networks and soils is a wide issue involving many communities from agronomy, soil science, biophysics to soil mechanics and civil engineering. Under non-stressful biological and chemical conditions, the root growth trajectory depends strongly on the mechanical strength of the soil and on the presence of obstacles at the root scale, as root apices must exert a growth pressure to overcome the resistance to deformation of the surrounding soil. Zones of high mechanical resistance are one of the most common physical limitations to soil exploration by roots, limiting the accessibility of the plant to water and nutrients. In turn, soil micro-structure is affected by the root development. Soil particles may be dragged by the root and, more generally, local soil deformations are induced by the root growth. The transfers of water between the soil and the plant as well as the root exudates and production of mucilage change locally the soil properties and modify the distribution of the aqueous phase in the porous network.  In addition, the mechanical properties of the soil are highly dependent on the root architecture, as the hierarchical structure formed by roots traps the soil and increases its resistance to shear, reinforcing the stability of slopes or limiting the erosion at river banks.

The objective of this session is to gather people around the mechanics of root-soil systems at different scales and with various experimental techniques, modelling or theoretical approaches: at the field scale to assess the contribution of plant roots to the mechanical stability of soil layers, at the scale of the root system for characterizing, simulating and imaging the whole root architecture and the reorganizations of the soil produced by the root growth, at the scale of the root apex to understand the mechanical feedback between a slender growing object and grains and pores of the soil matrix with given packing fractions and textures.

The session will consist of invited talks, nevertheless a slot will be kept for some flash talks (typically 4 min and 2 slides per speaker) providing an overview of the various research fields in the root-soil interaction. Proposals for communications as flash talks are welcome.

Session 3 “Computational methods in snow and avalanche release mechanics”  -2^nd October 2019

Coordinators : Johan Gaume (SLF Davos, Switzerland, johan.gaume@epfl.ch ), Pascal Hagenmuller (CEN, Météo-France , France, pascal.hagenmuller@meteo.fr ), François Nicot (IRSTEA, France, francois.nicot@irstea.fr ), Guillaume Chambon (IRSTEA, France, guillaume.chambon@irstea.fr )

Objectives:

This session aims at providing a thorough review of the current knowledge in snow and avalanche mechanics, spanning different scales from the snow microstructure to the slope scale associated with engineering issues.

Our present understanding of the mechanical processes leading to failure initiation and crack propagation in snow has significantly increased over the past decade, mostly by considering fracture mechanical approaches and micro-mechanical models. However, simulating snowpack instability at the slope-scale still remains extremely challenging, mostly due to the crucial importance of the snow microstructure. In this context, the objective of this session will be to present the current state of available methods applied at the different scales of interest, and to gather scientists developing numerical models to address snow and avalanche release mechanics. We plan to invite speakers having a large variety of backgrounds, from snow science, to fracture mechanics and numerical methods. The link between snow avalanches and landslides will be considered.

Program of the Workshop and school