Periodic pile barriers effectively attenuate surface waves induced by rail transit and similar sources and have become an important measure for environmental vibration mitigation. Existing studies on periodic pile barriers predominantly focus on real-part dispersion characteristics, while a systematic understanding of energy dissipation mechanisms remains limited. This study investigates hexagonally latticed locally resonant periodic pile barriers (HLRPPBs) through physical model tests, systematically examining the influence of the steel pipe pile outer radius (R o ) on the surface-wave attenuation zone (SWAZ). A three-dimensional finite-element model is subsequently developed based on the experimental parameters to compute complex dispersion relations. Energy storage density modes at band-edge points are extracted to elucidate the formation mechanism of the SWAZ under experimental conditions from a modal perspective. The experimental results indicate that, with the inner radius (R i ) held constant, increasing R o from 0.07 m to 0.09 m leads to a progressive reduction in the minimum value of the acceleration frequency response function (FRF). The lower band frequency (LBF) decreases, while the upper band frequency (UBF) increases. The pronounced upward shift of the UBF is identified as the primary contributor to bandgap widening. Modal analysis further reveals that, as R o increases from 0.07 m to 0.09 m, the formation mechanism of the UBF transitions from joint control by the matrix and the steel pipe pile core system to matrix-dominated control, whereas the LBF remains primarily governed by the steel pipe pile core system. These findings provide a theoretical basis for understanding the vibration isolation mechanisms of locally resonant periodic pile barriers with varying geometric parameters.
Liu et al. (2026) studied this question.