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Article Dans Une Revue Bulletin de la Société Géologique de France Année : 2013

Strain localization due to structural softening during pressure sensitive rate independent yielding

Résumé

After giving a complete analytical solution for the strain softening model associated to Mohr-Coulomb non associated elasto-plastic flow rule (MC-model), the paper demonstrates that this rheology possesses a finite limit load which allows solving for strength drop as a boundary value problem. The MC-model produces a non-dimensional strength drop, which depends on three parameters: the orientation of the shear band versus the least principal stress axis outside the band a 0 , the peak friction angle f and the dilatation angle Y. The maximum reduction of strength obtained with that strain-softening model is on the order of the confining stress p 0 . For this weakest regime, the effective friction of the shear band drops from µ ini = 0.85 at peak to µ ss = 0.64 at the end of the softening phase. In this model, which con-siders thick shear bands, the weakest regime is not obtained for an orientation corresponding to the exact Coulomb ori-entation. Instead, the orientation of the weakest shear zone systematically deviates from the coulomb orientation by an angle, which rises with its internal friction angle. The characteristic shear strain needed to achieve steady state is quanti-fied semi analytically and in the range of parameters valid for Earth, this strain is found to be of the order of 7-8%. These numbers are typical of what is observed in the laboratory, which give us confidence on that MC-model is a good and probably the simplest model to localize strain in numerical codes aimed at modeling the brittle part of the Earth. Localisation de la déformation causée par l'adoucissement structural durant la ruine de matériau dont la rhéologie dépend de la pression mais pas du taux de déformation
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Dates et versions

hal-01134794 , version 1 (24-03-2015)

Identifiants

Citer

Laetitia Le Pourhiet. Strain localization due to structural softening during pressure sensitive rate independent yielding. Bulletin de la Société Géologique de France, 2013, 184 (4-5), pp.357-371. ⟨10.2113/gssgfbull.184.4-5.357⟩. ⟨hal-01134794⟩
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