Empirical methods to quickly select an appropriate discrete fracture network (DFN) model representing the natural fracture facets

The accuracy of the established discrete fracture networks (DFNs) has a significant impact on the effectiveness of solving engineering problems, while the accuracy is affected by the selection of the model. Concerning the natural fracture facets, the existing method based on the Accuracy Representation Index (ARI) to select the circular or elliptical disc models is relatively complex, costly and time-consuming, and is not convenient for engineers at the field site. This study proposed two new empirical methods for engineers to quickly choose an appropriate model. The triangular, rectangular and diamond-shaped fractures are chosen as the basic shapes. For the fractures with other convex shapes, their ARI can be estimated on the basis of the three basic shapes. Moreover, a validation of a real case from an open-pit mine in the USA was made, three volunteers estimated the values of ARIc and ARIe of 56 fractures based on the proposed empirical methods, where ARIc and ARIe represent the values of ARI of circular and elliptical disc models, respectively, and the absolute error (er) from the empirical estimating method is calculated. The results show that the values of er are less than 0.1 and there is no obvious difference between results from the three volunteers. It illustrates that the proposed empirical methods are effective and applicable.