The Applicability of Two Pore Pressure Generation Models Developed for Sands to Fine-grained Soils

This study investigates the applicability of two pore pressure generation models—originally developed for clean sands—to soils containing both non-plastic and plastic fines. The models evaluated include the cycle-based formulation of Booker et al. and the energy-based formulation proposed by Green, Mitchell, and Polito. Their predictive capabilities were assessed using a comprehensive dataset comprising approximately 240 stress-controlled cyclic triaxial tests conducted on a wide range of soil types, including silty sands, sandy silts, silts, and clayey sands with varying fines contents and plasticity characteristics. The results indicate that both models provide highly accurate predictions of excess pore water pressure generation for soils containing non-plastic fines, regardless of whether the fines content is above or below the threshold fines content. The Booker et al. model demonstrated consistently strong performance across all soil types, with coefficients of determination (R 2 ) typically exceeding 0.95. Similarly, the GMP model exhibited excellent predictive accuracy for non-plastic soils, confirming the robustness of energy-based approaches under conditions dominated by contractive behavior and flow liquefaction. However, the performance of the two models diverges for soils containing plastic fines. While the Booker et al. model maintained high predictive accuracy for both low- and high-plasticity soils, the GMP model exhibited a systematic reduction in accuracy with increasing plasticity. This reduction is attributed to differences in deformation mechanisms, specifically the transition from flow liquefaction to cyclic mobility, which alters the relationship between dissipated energy and pore pressure generation. Overall, the findings demonstrate that simplified pore pressure generation models can be effectively extended beyond clean sands, particularly when appropriate calibration is employed. However, the results also highlight the importance of accounting for soil plasticity and deformation mechanisms, suggesting that modifications to energy-based formulations may be necessary to improve their applicability to soils exhibiting cyclic mobility.