The construction of civil works and in particular the excavation of underground cavitiesproduces strain, which in most cases develops partly instantaneously and partly in a delayedmanner. Consequently, rock damage and possible failure rarely occur instantaneously, butrather after a few hours or even years after the stress state has been modified as a result ofbuilding the structure. The first part of this report will therefore be devoted to experimentalresults, with a view to characterising the damageable viscoplastic behaviour of rocks. Theseinvolve mainly monotonic and cyclic creep, relaxation and quasi-static loading tests carried outin the laboratory and supplemented by observations of changes in rock microstructure. Thesecond part describes a constitutive model designed to reproduce the observed phenomena,taking into account in particular volume variations associated with viscoplastic strain andanisotropic damage. The last part describes the numerical simulation of underground structureexcavations, based on real, carefully instrumented cases. Particular emphasis is given to waysof simulating time-dependent changes in the damaged zone around underground storagecavities. To conclude, a number of prospective experimental and theoretical developments willbe outlined.
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