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Approach

This Montana Department of Transportation–sponsored Ph.D. research investigates the lateral load response of piles in low- to high-plasticity silt–clay mixtures representative of Montana soils using geotechnical centrifuge experiments. Instrumented model-scale pile is subjected to monotonic lateral loading, with a dense network of pore-pressure transducers embedded in the soil to capture excess pore-pressure generation, dissipation, and associated drainage effects. Miniature cone penetration tests performed in the centrifuge at varying penetration velocities further characterize drained-to-undrained soil response across mixtures with different plasticity indices.

Results

The centrifuge experiments produce a comprehensive dataset of pile deflections, bending moments, depth-dependent soil reactions, and excess pore-pressure evolution during lateral loading. Measurements from the pore-pressure transducer network and rate-controlled miniature CPTs reveal how drainage conditions and soil plasticity influence stiffness, mobilized resistance, and failure mechanisms. These results demonstrate systematic differences in lateral pile behavior across silt–clay mixtures that are not fully captured by existing p–y formulations, forming the experimental basis for developing p–y curves that explicitly account for plasticity and drainage effects.

Implications

This work advances the experimental understanding of laterally loaded pile behavior in intermediate soils, where drainage conditions and excess pore-pressure response play a critical role. The findings support the development of more representative p–y curves for transportation infrastructure founded in silt–clay mixtures, improving the reliability of lateral foundation design. The combined use of centrifuge pile tests, pore-pressure measurements, and rate-controlled CPTs provides a scalable framework for future studies and contributes to more informed geotechnical design practices for DOT applications.