Effects of grain breakage on hydraulic conductivity in granular soils under one-dimensional compression

Since hydraulic conductivity significantly influences the compression and deformation characteristics of granular terrains, this study examines the variations in permeability (k₂₀) of granular soils under one-dimensional compression. Two uniformly graded calcareous soil samples were tested: one with grain sizes of 9.50–12.70 mm, and another of 4.75–9.50 mm. Both samples were subjected to one-dimensional compression and constant-head permeability tests. Key soil properties affecting permeability (k₂₀), including absorption (n), specific surface area (S_s), relative density (D_r), void ratio (e), uniformity coefficient (C_u), effective grain size (d₁₀), and mean grain size (d₅₀), were analyzed. The virgin compression line (VCL) of the soil samples was identified within an oedometric stress (σ_VCL) range of 4.00–14.00 MPa, where the rate of change in soil properties affecting permeability was most pronounced. As oedometric stress increased, the instantaneous absorption (n_i) of the soil samples increased linearly, with a slope (α_n) of 0.055–0.061. Similarly, the instantaneous specific surface area (S_s,i) of the soil samples increased linearly, with a slope (α_s) of 1.229–1.388. In addition, practical equations were developed to predict the instantaneous relative density (D_r,i), instantaneous grain size distribution curve, and instantaneous permeability (k_20,i) of granular soils under one-dimensional compression.