991
General Report of TC 105
Geomechanics through the scales :
Rapport général du TC 105
La géomécanique à travers les échelles
Viggiani G.
UJF-Grenoble / Grenoble-INP / CNRS UMR 5521, Laboratoire 3SR, Grenoble, France
ABSTRACT: This general report presents and discusses the papers submitted to the Discussion Session of TC105 (Geomechanics
from Micro to Macro) at the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013. These papers
deal with a variety of issues and include experimental, analytical and numerical studies. Overall, they show that the theme of this
session is both challenging and promising. The discussion of the papers is preceded by some general remarks about the meaning,
trends and perspectives of research in geomechanics through the scales.
RÉSUMÉ : Ce rapport général passe en revue les articles soumis à la 18
ème
Conférence Internationale de Paris dans le cadre de la
session consacrée à la géomécanique de la micro à la macro échelle. Ces articles portent sur plusieurs thématiques, et comprennent
des études soit expérimentales, soit analytiques, soit numériques. Dans leur ensemble, ils montrent bien que le thème de cette session
est à la fois complexe et riche de perspectives. La discussion des articles est précédée par quelques considérations générales sur le
sens et les perspectives actuelles de la recherche dans ce domaine.
KEYWORDS: geomechanics through the scales, experiments, analytical and numerical studies.
1 INTRODUCTION
This general report briefly presents the 15 papers that were
submitted to the Discussion Session of TC105 (Geomechanics
from Micro to Macro) at the 18
th
International Conference on
Soil Mechanics and Geotechnical Engineering, Paris 2013.
While only 6 papers have been actually selected for oral
presentation, all 15 can be found in these proceedings. The
focus of this session is on new advances in geomechanics
through the scales – from micro to macro – and it encompasses
many aspects of geomechanics and geotechnical engineering,
from fundamental modeling and laboratory experimental studies
to more applied topics and recent challenges related to the
safeguard of the environment and the production of energy.
Table 1 lists the papers belonging to the session. In the
report, the papers will be presented and discussed in the order
adopted in Table 1. Citations of papers belonging to this session
will be mentioned in Italics in the text. These papers might be
grouped into different tracks, depending on whether they are
categorized by material studied (fine-grained
vs.
coarse-grained
geomaterials), approach of the study (experimental, numerical
and analytical) or application (petroleum, energy, civil …). In
this report, we have rather decided to discuss papers depending
on whether they are actually dealing with both the micro and the
macro scale, or just focusing either on the micro or the macro
scale. The discussion of the papers is preceded by a short
summary of the activities of TC105, followed by some general
comments about the meaning, trends and perspectives of
research in geomechanics through the scales.
2 GEOMECHANICS FROM MICRO TO MACRO
2.1
A short summary of the activities of TC105
At the 15
th
ICSMGE in Istanbul (2001) a technical committee
was appointed (at that time TC35, now TC105) to promote
scientific research on the behavior of geomaterials at the micro
scale, so as to clarify the fundamental micromechanisms
responsible for behavior observed at higher scales. Since then,
the study of the behavior of geomaterials (soils and rocks)
through different scales – from micro to macro – has become an
emerging field in our community, along with the increasing
awareness of the need of integrating these different scales –
which is increasingly possible thanks to major advances in both
the experimental and computational tools available.
Three specific conferences have been organized by the
technical committee TC105 (IS-Yamaguchi in 2006, IS-
Shanghai in 2010 and IS-Hong Kong in 2013), and a fourth
conference will take place in Cambridge in 2014. Furthermore,
a themed issue for Géotechnique (entitled “Soil mechanics at
the grain scale”) appeared in 2010, followed by a themed issue
for Géotechnique Letters (entitled “Geomechanics across the
scales”) in 2012.
2.2
General considerations
Geomaterials are rich in features interacting across the scales –
from asperity size to grain size, from the length of force chains
to the thickness of shear bands, and from laboratory specimens
to the full geotechnical engineering scale. Geomaterials exhibit
multi-scale behavior that is intrinsically associated with the
interactions of the individual particles (see for example the
magnificent review paper by Santamarina 2003). Large-scale
geotechnical engineering could gain so much from accurate
description of the relevant features exhibited at the finer scales.
The “father” of our discipline, Karl Terzaghi, already
reflected on this matter back in 1920:
‘[Coulomb] purposely
ignored the fact that sand consists of individual grains.
Coulomb’s idea proved very useful as a working hypothesis, but
it developed into an obstacle against further progress as soon
as its hypothetical character came to be forgotten by Coulomb’s
successors. [. . .] The way out of the difficulty lies in dropping
the old fundamental principles and starting again from the
elementary fact that sand consists of individual grains
’. Ever
since, Terzaghi’s words were not forgotten. The consideration
of the behavior of geomaterials from the most basic units,
i.e
.,
the particles, has in fact been the
raison d’être
of
