Abstract: Due to the diverse particle composition and complex formation processes of gravelly soils,the distribution pattern and calculation method for horizontal soil resistance still require further investigation. This study conducted lateral plate loading tests on gravelly soils using a two-dimensional geomechanical simulation bench. The relationship between horizontal ultimate resistance and displacement at varying depths was examined,and a simplified calculation method for resistance was proposed. The results indicate that soil resistance increases linearly with load initially,followed by a nonlinear steep increase and finally stabilizes. The ultimate horizontal resistance(p_max)is significantly influenced by depth(z)and soil relative density(D_r),showing a proportional increase with both. Based on the characteristics of ultimate resistance-displacement-depth variation and applying the Fleming normalization relationship between p_max,z,and the lateral pressure coefficient K_p,this study investigated the effect of D_r on parameters such as curve slope and position in the characterizing equation. A simplified calculation method for the horizontal ultimate resistance of gravelly soils based on lateral plate load test data is proposed. The difference between calculated values using this method and measured ultimate load values is within 10%,showing good agreement. These findings contribute to the theory of foundation design for building structures and support more scientific and rigorous reliability assessments of pile-soil systems.