Viscoplasticité et endommagement des roches en application à la modélisation du comportement à long terme des ouvrages souterrains
Résumé
The construction of civil works and in particular the excavation of underground cavities
produces strain, which in most cases develops partly instantaneously and partly in a delayed
manner. Consequently, rock damage and possible failure rarely occur instantaneously, but
rather after a few hours or even years after the stress state has been modified as a result of
building the structure. The first part of this report will therefore be devoted to experimental
results, with a view to characterising the damageable viscoplastic behaviour of rocks. These
involve mainly monotonic and cyclic creep, relaxation and quasi-static loading tests carried out
in the laboratory and supplemented by observations of changes in rock microstructure. The
second part describes a constitutive model designed to reproduce the observed phenomena,
taking into account in particular volume variations associated with viscoplastic strain and
anisotropic damage. The last part describes the numerical simulation of underground structure
excavations, based on real, carefully instrumented cases. Particular emphasis is given to ways
of simulating time-dependent changes in the damaged zone around underground storage
cavities. To conclude, a number of prospective experimental and theoretical developments will
be outlined.