Transverse Isotropic Strength Criterion and Parameter Identification Method for Carbonaceous Slate
To study the transverse isotropic mechanical properties of layered rock,the strength criterion and parameter identification method for carboniferous slate were studied by using laboratory test and theoretical analysis.First,the conventional uniaxial and triaxial compression tests with different confining pressures were carried out on horizontal and vertical stratified rock samples to investigate the strength characteristics and failure modes of carboniferous slates under different stress states.Second,the transversely isotropic elastoplastic constitutive model for carbonaceous slate was established by comparing and analyzing the experimental results.The yield function of model was determined based on the Pariseau strength criterion to describe the strength characteristics of carboniferous slate in different directions.The plastic potential function of model was determined based on the associated flow rule to describe the flow direction in the plastic deformation stage of carbonaceous slate.Under the assumption of isotropy,the model can be degraded to Drucker-Prager model for describing isotropic geotechnical materials.Finally,the identification method of model parameters was proposed,in which the elastic parameters were solved by conventional triaxial compression test and empirical formula;the compressive,tensile and shear strengths of rock samples were determined with the least square method based on Duveau numerical calculation program,conventional triaxial tests,and linear Mohr-Coulomb criterion.Then the plastic parameters were solved by substituting them into the derived formulas.The rationality of proposed transverse isotropic strength criterion was verified by combining the experimental results.The result indicates that the compressive strengths of horizontal rock samples under different confining pressures were higher than those of vertical rock samples;the compressive strength increases linearly with the increase of confining pressure.The carbonaceous slate is usually brittle failure during compression,the horizontal bedding rock is slip-shear,and the vertical bedding rock is tensile-shear.
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