Directional Propagation of Traffic–Induced Vibrations and Local Wall–Soil Response in a Bridge–Sluice System: Field Testing and Numerical Analysis

–Bridge–sluice systems serve road traffic and hydraulic regulation, yet the directional association of traffic–induced vibrations within the bridge deck—sluice pier—embankment system and its implications for –wall–soil interaction remain insufficiently understood. Synchronized field measurements were conducted at the Wucun control sluice using four vehicle types and multiple speeds. Transfer entropy (TE) was used to identify directional information associations rather than amplitude– or energy –transmission ratios, and measured horizontal and vertical velocity histories were converted into phase–consistent displacement inputs for a two–dimensional –wall–soil model. Vibration amplitudes varied non–monotonically with speed, indicating that vehicle mass alone did not govern the response. The crawler excavator generated vertical and horizontal bridge–deck peak–to–peak velocities of 22.549 and 26.334 mm/s, respectively. The dominant information pathway was bridge deck to sluice pier to embankment; the crawler excavator produced the strong–est transfer, with a pier–to–embankment retention coefficient of 0.81. Within the adopted two–dimensional numerical idealization, the backfill was predicted to remain predominantly elastic at the measured vibration level, with response concentrations at side–wall corners and adjacent contact zones, particularly near the upper corner of contact zone B. Local plasticity first emerged at 10 times the measured input and expanded over the 15–25–fold range. These findings support control of high–impact vehicles and targeted monitoring of side–wall—embankment connections where deformation incompatibility and seepage –control risk may concentrate.