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 ARI_c and ARI_e of 56 fractures based on the proposed empirical methods, where ARI_c and ARI_e 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.

建立的离散裂缝网络（DFN）的准确性对解决工程问题的有效性有重要影响，而准确性受模型选择的影响。关于天然裂缝面，现有的基于精度表示指数（ARI）的圆形或椭圆形圆盘模型的选择方法相对复杂，昂贵且费时，并且对于现场工程师而言并不方便。这项研究提出了两种新的经验方法，供工程师快速选择合适的模型。选择三角形，矩形和菱形裂缝作为基本形状。对于其他凸形裂缝，其ARI可以根据三个基本形状进行估算。此外，从美国的露天矿制成一个真实的案例的验证，三名志愿者估计的值ARI _Ç和ARI _Ë基础上提出的经验方法，其中的56个骨折ARI _Ç和ARI _Ë表示值分别计算圆盘和椭圆盘模型的ARI，并根据经验估计方法计算绝对误差（er）。结果表明er的值小于0.1，并且三名志愿者的结果之间没有明显差异。这说明所提出的经验方法是有效和适用的。