Identification of material parameters for numerical simulation of the behavior of rocks under true triaxial conditions

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I.G.Sakhno, Dr. Sc. (Tech.), Assoc. Prof.,, State Higher Educational Institution “Donetsk National Technical University”, Pokrovsk, Ukraine, e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

А.V.Molodetskyi, Cand. Sc. (Tech.),, Institute for Physics of Mining Processes National Academy of Sciences of Ukraine, Dnipro, Ukraine

S.V.Sаkhno,, State Higher Educational Institution “Donetsk National Technical University”, Pokrovsk, Ukraine, e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.


Purpose. Development a modified model of geomaterials for numerical simulation of the behavior of rocks in a true triaxial stress field.

Methodology. The research was conducted on specimens of coal grade “С”. Input parameters of materials for basic models in the modeling by the finite element method were taken from the physical experiment. The experiment was conducted on the installation of true triaxial compression. The results of comparative studies on the behavior of rocks in the true triaxial stress field using the experimental method and numerical mathematical modeling are presented. Modeling is conducted by the finite element method in Ansys Inc software. The results of tests on the strength of coal specimens in generalized compression conditions are taken as in-situ properties.

Findings. It is established that use of classical deformation models – the elastic model and Drucker–Prager model – with numerical mathematical modeling of geomechanical processes is in error when describing the behavior of geomaterials in a volumetric field of stress of 30–15 % relative to the experiment. In this case, modeling with the use of an elastic model does not only cause a significant quantitative error, but also fails to reflect the quality of the dependence of the Young module and the volume compression module on average stresses at all stages of the strain. To adequately imitate the model of geomaterials, one must take into account the anisotropy of the elastic modulus, the shear modulus and the coefficient of transverse deformation, as well as the functional dependence of the dilation from the plastic deformation and the coefficient of rigidity.

Originality. The Drucker–Prager model was modified by taking into account the anisotropy of coal properties. Depending on the “average stress-average deformation”, the calculation error for the elastic model is 33 %, for the Drucker-Prager model it is 15 %, while for the modified Drucker–Prager model it is 0.14 %.

Practical value. Using the results of the study can improve the accuracy of the prediction the stress-strain state of geomechanical objects.


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Tags: finite element methodgeomaterial modelingelastic modelDrucker–Prager modelstressdeformation

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