ABSTRACT

Viscoplasticity in Rock Mechanics P.BEREST

Laboratoire de Mécanique des Solides, École Polytechnique, Palaiseau, France

1 LABORATORY TESTS

Delayed effects can easily be observed in most underground works. In such works, it is the opening of galleries or cavities which constitutes, by itself, the mechanical load; from experience it is known that, when digging stops, deformation of the gallery still goes on. The most spectacular proof of delayed effects appears in evaporite deposits (rock salt or potash) or very soft rock masses (clay), but no rock exists for which such effects are completely missing. They are acting over months and sometimes years. They set the designer a difficult problem, for he cannot deduce the ultimate behaviour of the opening from observations which can be made during the construction period.