A visco-elastic rheological model is first illustrated which accounts for the so called primary (reversible) and secondary (plastic) components of the creep deformation. The model is subsequently extended to introduce the effects of tertiary creep. This is done by considering the reduction of shear strength, and apparent viscosity, of the rock with increasing shear deformation, after the onset condition has been reached. Two alternative conditions for the initiation of tertiary creep are discussed. They are directly derived from those adopted in time-independent, strain softening analyses for detecting the onset of the so called shear bands, and the consequent loss of the mechanical resistance of the rock element.
A visco-elastic …
AUTORI: Sterpi D., Gioda G. RIG ANNO: 1999 NUMERO: 1 Numero di pagina: 59