Cumulative Settlement of Pile Group Under Cyclic High-Speed Train Loading-Paper

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The study uses three-dimensional finite-element analysis in ABAQUS to estimate cumulative settlement of single piles and pile groups under cyclic loading representative of high-speed train traffic. The models represent piles and pile caps as elastic concrete and the surrounding clay with a Mohr–Coulomb plasticity model. They are validated against published single-pile and pile-group experiments, with reported settlement deviations below 5%. Analyses examine train speed, pile length-to-diameter ratio (L/D), pile-to-soil stiffness ratio, pile spacing (S/D), and pile-cap thickness over up to 10,000 loading cycles.<br /><br />Settlement develops rapidly during early cycles, then accumulates more slowly. Train speed has little influence on ultimate settlement in the cases studied, although initial settlement is greater at lower speeds. Increasing pile length reduces settlement, attributed to greater shaft resistance and anchorage; the authors identify an L/D corresponding to a 60 m pile as effective, while noting that longer piles may not be economical. Stiffer soil also reduces settlement. The paper’s discussion indicates that increasing the pile-to-soil stiffness ratio by lowering soil stiffness increases settlement.<br /><br />For pile groups, spacing around three pile diameters is recommended: larger spacing increases settlement and requires a larger pile cap. Increasing pile-cap thickness reduces settlement, but the benefit diminishes at greater thickness, making a normalized thickness parameter of about 15 a proposed economical choice.<br /><br />Overall, the study highlights the importance of balancing settlement control and construction cost when designing pile foundations for high-speed railway viaducts. Its findings are based on numerical models with simplified, homogeneous soil assumptions and should be interpreted accordingly.

Keywords

finite element analysis

ABAQUS

cumulative settlement

cyclic loading

high-speed train traffic

pile foundations

Mohr-Coulomb plasticity

pile groups

pile spacing

pile-cap thickness