Study on the Mechanism of Rock Brazilian Disk Splitting Based on the Constitutive Model With Different Tensile and Compressive Moduli

Due to the significant tension–compression asymmetry of rocks, the disparity between the results of Brazilian splitting tests and those derived from the linear elastic constitutive theory has been a topic of extensive discussion. In order to delve into the stress–strain field evolution and crack propagation process of Brazilian splitting tests under tension–compression varying modulus constitutive models, finite element software was employed. By means of self-developed subroutines, a method was employed to control the rock’s tension and compression with different modulus. Comparative analysis was conducted to scrutinize the distinctions between linear elastic constitutive models and variational modulus constitutive models. The results elucidate that under the variational modulus constitutive model: (1) Stress concentration in the x-direction does not occur at the center of the rock but is offset toward the two sides of the rock loading end, with stress peaks similar to linear elasticity; (2) under the variable modulus constitutive model, shear effects are pronounced at both ends of the rock loading axis, and initial cracks in the rock originate near the two sides of the loading end, forming initial cracks of tensile-shear mixed mode; and (3) due to the influence of shear stresses at both ends of the rock loading, the ultimate load of the rock is lower than that of a linear elastic structure, and the calculated tensile strength is lower than the true strength of the rock.