Sensitivity Analysis of the Micro-Parameters Used in a PFC Analysis Towards the Mechanical Properties of Rocks

Reproduction on complex behavior of rocks in actual case studies is undoubtedly the main aim of numerical modelling applied to rock mechanics. However, to achieve a reliably realistic simulation process a good knowledge of rock behavior is needed together with calibration or matching processes of actual and controlled tests on rock. Within this framework, in a previous approach, the authors calibrated PFC (Particle Flow Code) micromechanical parameters to reproduce in a reasonably accurate way the complete stress-strain response of granite samples under triaxial conditions in the lab. In this previous study, it was found that the number of different micro-parameters needed to define a PFC model was large, and that the influence of some of these parameters on rock response was not clear. In this new study, a sensitivity program is carried out in order to assess the influence of micro-mechanic parameters on the macroscopic response of the numerical simulation of rock samples. The sensitivity approach carried out shows that there is a direct connection between some parameters, for example, the bond cohesion and the bond tensile strength influences the peak strength and tensile strength of the rock, respectively. However, it is not clear how these parameters may influence other geomechanical macro properties, neither the exact influence of other parameters as the friction coefficient or the stiffness ratio. The present study addresses some of these issues, and it sheds light on which are most relevant parameters and how they control the main macro-properties of the simulated rocks.