Abstract A novel model combined with fractal theory and the discrete fracture network (DFN) model is proposed to simulate radon migration in fractured media. In the novel model, the fracture center and length distribution are determined by a first-order model, and the fracture orientations are modeled with the von Mises-Fisher distribution. The model is further developed into a computer software that can calculate the radon diffusion coefficient and exhalation rate of fractured media. An outcrop map is used to validate the ability of the model to describe complex fractures, and radon migration in natural fractures at an outcrop site is predicted using the model. Results show that the model has good reliability and robustness. Evaluation of the representative elementary volume (REV) indicates the existence of REV during the modeling of radon migration in fracture networks. Following an exponential law, REV size decreases with the increase in the length exponent.

中文翻译：

---

用于分析裂隙介质中氡迁移的分形离散裂隙网络模型

摘要 提出了一种结合分形理论和离散裂缝网络（DFN）模型的新型模型来模拟裂缝介质中氡迁移。在新模型中，裂缝中心和长度分布由一阶模型确定，裂缝方向用 von Mises-Fisher 分布建模。该模型进一步发展成计算机软件，可以计算裂隙介质的氡扩散系数和呼出速率。露头图用于验证模型描述复杂裂缝的能力，并使用该模型预测露头地点天然裂缝中的氡迁移。结果表明，该模型具有良好的可靠性和鲁棒性。对代表性基本体积 (REV) 的评估表明在裂缝网络中氡迁移建模过程中存在 REV。遵循指数规律，REV 大小随着长度指数的增加而减小。