Abstract: To investigate the evolution of permeability characteristics of geotextile materials in woven soilbags under compressive deformation in hydraulic protection engineering, a self-developed vertical permeability device and image analysis were utilized to study pore structure and seepage behavior under 0%−10% uniaxial tensile strain. The results demonstrated that tensile strain has a significant impact on the pore distribution of soilbag geotextiles. Porosity exhibited a weak exponential increase, while specific surface area showed a weak logarithmic increase with tensile strain. These relationships were quantified using a woven geotextile single-pore model. The hydraulic gradient-velocity relationship during seepage conformed to the Forchheimer equation. The critical Reynolds number exhibited non-monotonic variation, decreasing initially and then increasing with tensile strain. Inter-fiber spacing significantly influences flow regime transitions under low tensile strain. Based on the flow regime classification, the permeability coefficient corresponding to the Darcy flow regime was extracted. A predictive model for the permeability coefficient under tensile deformation was developed using porosity and specific surface area as predictors. The model’s predictions showed good agreement with experimental measurements. The study elucidates the underlying mechanism by which tensile strain modulates the permeability of soilbag geotextiles through changes in porosity and specific surface area.

Key words: soilbag, tensile loading, morphological parameters, critical Reynolds number, permeability coefficient