Topology reorganization in discrete fracture networks: Effects of geometric representation and preferential elongation on permeability

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Abstract
How pore-network geometry controls fluid transport remains a central question in confined flow through disordered media. This study investigates how alternative fracture-shape representations reorganize conductive-network topology and are associated with different permeability responses under comparable fracture-intensity conditions. Discrete fracture networks are treated as geometrically controllable pore-network analogs and mapped into node–edge networks using conversion procedures developed for curved-boundary and polygonal fracture geometries. Using rectangular fracture networks as references, circular disk, similar elliptical disk, and universal elliptical disk (UED) representations are compared. Equivalent permeability is calculated independently using FracMan, whereas graph descriptors are derived separately from the corresponding intersection networks. Based on five independent realizations, the UED model shows the closest agreement with the reference network in both topology preservation and permeability consistency, while the circular disk model exhibits the largest deviation. For non-equidimensional fractures under fixed intensity and orientation conditions, preferential elongation generates permeability anisotropy and a non-monotonic response along the preferential direction. Although the abundance of fracture intersections increases continuously with elongation, permeability initially increases and subsequently decreases. Changes in local pathway redundancy and backbone persistence suggest that moderate elongation promotes the formation of directionally aligned conductive pathways, whereas excessive elongation disrupts this organization by reducing pathway redundancy and replacing a substantial proportion of topologically important fractures. These findings demonstrate that comparable fracture intensity does not ensure topological or hydraulic equivalence and support a topology-based interpretation of representation-dependent, anisotropic, and non-monotonic transport behavior.
Funding Information
  • Natural Science Foundation of Fujian Province (2025J08001)
  • Natural Science Foundation of Xiamen Municipality (3502Z202471008)
  • Fundamental Research Funds for the Central Universities (20720250112)

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