Study on the correlation of macro and meso parameters of parallel bond model sandstone

Abstract

In order to study the mechanical response and failure characteristics of sandstone at the meso level, this paper first carried out indoor rock compression test and PFC2D uniaxial macro-meso parameter correlation numerical test based on parallel bond model.Then, the trial-and-error method is used to determine the order of the influence degree of each mesoscopic parameter on the macroscopic mechanical index, and the interaction analysis of significant factors is carried out.Finally, the regression analysis is used to establish the functional relationship between macroscopic and mesoscopic parameters.The main influencing factors of crack evolution and failure mode of rock samples are studied by using the control variable method.The results show that: ①The uniaxial compressive strength σc has a complex nonlinear relationship with parallel cohesion c, bond normal strength σc and bond internal friction angle φ.; ② Elastic modulus E has a polynomial relationship with bond modulus E * and bond stiffness ratio k *; ③ Poisson's ratio v is linear with k * and friction coefficient μ; ④The tensile strength σt has a good linear relationship with c and σc.; ⑤The crack evolution and failure mode of rock samples are mainly affected by the bond strength ratio σc/c, which is negatively correlated with the number of tensile cracks and positively correlated with the number of shear cracks. With σc/c increases, the failure mode of rock samples is characterized by tensile failure-conjugate failure-shear failure.The evolution law and failure form of uniaxial compression σ-ε in laboratory test and numerical simulation are basically the same.

Keywords

• pfc2d
• uniaxial compression
• trial and error method
• regression analysis
• control variable method
• form of destruction