AbstractExcess pore pressure generation of uniform gravel and gravel-sand mixtures was evaluated in this study. Comparisons were made with existing relationships for pore pressure generation of sands and show that gravel and gravel-sand mixtures can exhibit different pore pressure responses. The influence of liquefaction definition, gravel particle angularity, particle size, relative density, initial vertical effective stress, cyclic stress ratio, and gravel percentage, on the generation of excess pore water pressure of gravel and gravel-sand mixtures was studied. Liquefaction definition, particle size, initial vertical effective stress, and cyclic stress ratio were found to not have a significant effect on the normalized excess pore pressure generation (i.e., ru versus N/NL). Conversely, relative density, particle angularity, and mixture percentage of gravels were found to have a more significant effect on the normalized excess pore pressure generation response (i.e., ru versus N/NL). Additionally, the coefficient of uniformity (Cu) was found to have a strong correlation with increased excess pore pressure generation ratio at values of N/NL less than 0.40, highlighting the influence of grain size distribution on early pore pressure generation response. A new pore pressure model was developed to predict ru based on Cu for gravelly soils.