Due to severe mass transfer limitations, contaminated soils with low-permeability limit the accessibility of amendments, resulting in less effective or even ineffective remediation. Enhancing the mass transfer properties of low-permeability soils by hydraulic fracturing is a promising technique. A quasi-three-dimensional (quasi-3D) analytical model was presented that accounted for advection-diffusion-adsorption-degradation processes in the fracture-matrix system. The model combined the injection-extraction technique to investigate the enhanced transport of amendments in low-permeability contaminated soil by hydraulic fractures. Then, the injection strategy and controllable parameter optimization were comprehensively studied by analyzing the radial transport behavior of the amendment within hydraulic fractures. The results showed that higher injection volumetric rates accelerated the formation of a uniform line source within the fractures. Although the differences in the effective ratio of the amendment among different injection modes were not significant, considering the amendment utilization rate and cost reduction, the recommended injection strategy was the combination of continuous pulsing injection and periodic injection.

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Keywords: Low-permeability soil, Hydraulic fracturing, Enhanced remediation, Injection-extraction technology, Analytical solution