Sensitivity Analysis of Macroscopic Mechanical Behavior to Microscopic Parameters Based on PFC Simulation

PFC is based on discrete element theory and has become essential for simulating rock mechanical behaviour. In PFC, the microscopic mechanical behaviour of the ball is the crucial factor that determines the macroscopic mechanical state. This study used a quantitative analysis method to conduct a uniaxial compression experiment in PFC. The comparative analysis of macro-mechanical properties under the influence of micro-parameters was carried out. The macroscopic mechanical properties were the stress–strain curve, strength, elastic modulus, crack development, and failure. This simulation used microscopic parameters such as contact stiffness, parallel-bond modulus, ball and bond stiffness ratio, and ball friction coefficient as single-factor variables. The results showed that the sensitivity of elastic modulus to contact stiffness, parallel-bond modulus, and bond stiffness was significantly higher than that of the ball stiffness ratio and ball friction coefficient. The contact stiffness and the parallel-bond modulus were linearly related to the elastic modulus. There was an exponential relationship between parallel-bond stiffness and elastic modulus. When the load on the model was close to the peak strength, shear cracks were mainly generated, including single shear fracture and multiple shear fracture. However, tensile cracks were developed locally in the model. The change of micro parameters had a limited impact on the fracture type and macro fracture location.