GEOPHYSICAL RESEARCH, 2018, vol. 19, no. 3, pp. 57-72. https://doi.org/10.21455/gr2018.3-4

UDC 539.3, 539.4.01

Abstract  References   Full text (in Russian)   Full text (in English)  

ESTIMATION OF ROCK STRENGTH PROPERTIES FROM TRIAXIAL TEST DATA

I.A. Garagash(1), N.V. Dubinya(1), O.A. Rusina(1,2), S.A. Tikhotsky(1), I.V. Fokin(1)

(1) Schmidt Institute of Physics of the Earth, the Russian Academy of Sciences, Moscow, Russia

(2) Lomonosov Moscow State University, Moscow, Russia

Abstract. The article is devoted to usage of non-associated plastic flow law for describing deformation processes occurring in rock masses subjected to external stresses. The constitutive relations are formulated for a rock mass being subjected to stresses exceeding its elasticity limit. The concept of friction angle being a function of accumulated plastic strain is used to describe deformation process. The experimentally obtained stress-strain curves provided by series of triaxial tests carried out for fractured rock samples are considered within the formulated model. It is shown that usage of non-associated plastic flow law gives an opportunity to describe the experimental results more precisely compared to standard methods such as Mohr–Coulomb model. Numerical simulation presented in the article provides an image of plastic deformation localization taking place in rocks in natural conditions. The physical mechanism of plastic deformation accumulation through emerging fractures and reactivation and propagation of pre-existing fractures is proposed. The fracture system evolution model tendency is revealed for conditions of triaxial test: it is shown that propagating fractures are to be specifically spatially oriented as the angle between normal vectors to them and the symmetry axis can be calculated. As far as the concept of changing friction angle is used, the spatial orientations and relative number of propagating fractures in rock masses can be qualitatively and quantitatively determined at each moment of deformation process. The proposed model of fractured rocks' deformation under applied external stresses tested using experimental data can be used for a more precise description of rheology while dealing with geomechanical problems.

Keywords: geomechanical modeling, strength properties of rocks, nonassociated law of plastic flow, variable angle of internal friction.

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