Abstract: Variable control method is used to comprehensively analyze the influence of all the microscopic parameters of parallel bond model on its macroscopic parameters, They are mainly manifested as: Parallel-bond modulus and particle contact modulus Ec are the main controlling factors of macro elastic modulus and there is a linear relationship between them. The Poisson's ratio is mainly affected by the particle stiffness ratio kn /ks and the parallel bond stiffness ratio and there is a logarithmic relationship between them. The bond strength of the particle bond determines the strength properties of the material. The cohesion c and tensile strength of interior materials are mainly influenced by the parallel-bond normal strength and the parallel-bond strength ratio ; they increase linearly with the parallel-bond normal strength and decrease logarithmically with the parallel-bond strength ratio 。 The friction angle is mainly affected by the friction coefficient u of the particles, and the two are in a logarithmic relationship. Analysis of fracture propagation characteristics shows that the relative sizes of the material's normal and tangential bond strengths determine the distribution of cracks. With the increase of parallel-bond strength ratio , the tensile failure area of the rock sample decreases, while the shear zone increases, and the failure surface breaks from the shear failure to conjugate damage. The smaller the dispersion of the strength of the material, the rock sample tends to focus on the destruction, the destruction of the surface is obvious, the ratio between the mean and the standard deviation of the parallel bond strengths more than 3.5 is appropriate; with the increase of parallel-bond stiffness ratio , the macroscopic damage develops to conjugate destruction. In addition to matching the strength parameters, the mesoscopic parameters need to consider the consistency of the failure modes. Considering the mutual influence of multiple parameters, the empirical formulas between the macro and meso parameters are established, the mesoscopic parameters are selected and optimized, and examples are verified. The values of peak loads, deformation parameters and shear strength obtained by indoor tests and numerical simulations are close to each other. The stress-strain evolution law is the same and the damage patterns are the same, indicating that the mesoscopic parameter results are reliable.

Key words: numerical analysis, parallel bond model, macroscopic properties, mesoscopic parameters, correlation