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Article Dans Une Revue Journal of the Mechanics and Physics of Solids Année : 2016

Dependence of rock properties on the Lode angle: Experimental data, constitutive model, and bifurcation analysis

Alexandre I. Chemenda
D. Mas
  • Fonction : Auteur

Résumé

The overwhelming majority of experimental tests on rocks have only been conducted for a single value of the Lode angle θθ corresponding to the axisymmetric compression (AC). There are now sufficiently extensive data sets from both AC and axisymmetric extension (AE) tests (corresponding to two extreme θθ values) for two materials (synthetic rock analog GRAM1 and Solnhofen Limestone). These data cover a wide range of the confining pressure (from brittle faulting to ductile flow). Very recently the data from true 3-D tests (for different θθ) also covering both brittle and ductile fields were published for Castlegate and Bentheim Sandstone as well. The results from all these tests summarized and processed in this paper constitute a solid basis which allows general conclusions to be drawn about the dependence of rock behavior on θθ. In all cases, the yield/failure envelopes were shown to be θθ-dependent so that the material strength at low mean stress σσ is smaller under AE than under AC, while at high σσ, it is the opposite. The brittle-ductile transition under AE occurs at σσ ~1.5 times greater than under AC, meaning that under AE the material is more prone to fracture development. The angle between the most compressive stress and the forming deformation localization bands is systematically higher for AE than for AC for the same σσ. Based on these data we formulate a new three-invariant constitutive model with convex and concave yield functions (YFs) which is used for the bifurcation analysis. The results of this analysis agree with the experimental data (for both YFs) and reveal that the θ -dependence of rock properties encourages the strain localization. The major factors defining this dependence are the θθ-dependence of the YFs but also of the dilatancy factor which is greater for AE than for AC. The theoretical results show that the failure (deformation band) plane can deviate from the intermediate stress direction and can become parallel to the maximum compressive stress at high σσ for the concave YF.
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Dates et versions

hal-01401420 , version 1 (23-11-2016)

Identifiants

Citer

Alexandre I. Chemenda, D. Mas. Dependence of rock properties on the Lode angle: Experimental data, constitutive model, and bifurcation analysis. Journal of the Mechanics and Physics of Solids, 2016, 96, pp.477 - 496. ⟨10.1016/j.jmps.2016.08.004⟩. ⟨hal-01401420⟩
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