<p>Centrifuge modeling provides an effective means of physically simulating soil behavior under stresses equivalent to those in the field; however, the scaling law governing seepage-induced failure in gap-graded granular soils remains insufficiently understood. This study first develops a scaling law for uniformly graded granular soils based on particle-scale force equilibrium, ensuring that the critical hydraulic gradient is identical in both the centrifuge model and the 1g prototype when particle sizes are uniform or the gap ratio is small (less than 4). Coupled discrete element method (DEM) simulations were then performed to validate the proposed scaling law. The results indicate that, for soils with a gap ratio greater than 4, discrepancies in the critical hydraulic gradient between the centrifuge model and the prototype arise from the uneven stress distribution between coarse and fine particles, a mechanism that is also influenced by the g-level. To quantify the difference in contact forces between coarse and fine particles at the critical hydraulic gradient, a critical stress-reduction factor is introduced to quantify these differences and is correlated with both gap ratio and g-level. Finally, a generalized scaling law is established and validated by DEM simulations.</p>