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

Abstract

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.

Numerical Studies of Floor Heave Control in Deep Mining Roadways with Soft Rocks by the Rock Bolts Reinforcement Technology

“…Te results of laboratory tests show that the failure strain of mudstone is 0.018-0.02, and of the coal is 0.012-0.016 (Figure 3). Tis corresponds with the results of testing soft rock specimens in a volumetric feld [36][37][38] and under uniaxial compression [39,40]. According to the results of tests, it was found that for mudstone, siltstone, argillite, and sandstone with uniaxial strength of 25-40 MPa, the failure criteria for strain is about 0.02-0.03.…”

Numerical simulation of the surface subsidence evolution caused by the flooding of the longwall goaf during excavation of thin coal seams

“…At the same time, the rocks were modeled as heterogeneous. The variation of the physical and mechanical properties of rocks along and across the layering was determined according to the methodology proposed Sakhno et al [29], which is generally consistent with the research of Rzhevsky.…”

Stress environment around head entries with pillarless gobside entry retaining through numerical simulation incorporating the two type of filling wall

“…In the numerical simulation model, the thickness of coal seam is 1.5 m. The immediate roof was To simulate the behavior of rocks, a Drucker-Prager deformation model was used. The adequacy of the deformation model was established by simulation experiments [26]. According to the described structure, each layer was assigned a deformation modulus, Poisson's ratio, an angle of internal friction, an adhesion coefficient, and a dilatancy angle (table 1).…”