Spatial Vibration Response and Energy Distribution Characteristics of Soil-Rock Mixed-Fill Subgrade during Sequential Vibratory Compaction

The vibration field generated during vibratory compaction is critical for revealing the compaction mechanism of subgrade. To analyze the vibration response characteristics of subgrade under different vibration conditions, this study conducted field vibratory compaction tests, collected subgrade vibration signals under weak vibration and strong vibration conditions, and analyzed them from the perspectives of the time domain, frequency domain, and spatial energy distribution. The results show that, during successive rolling passes, the acceleration response in the strong vibration stage was generally higher than that in the weak vibration stage. The frequency-domain response of the subgrade was mainly controlled by the excitation frequency of the vibratory roller, and the spectral centroid and effective bandwidth fluctuated with the number of rolling passes. Peak acceleration in the Z direction showed a relatively strong positive correlation with the measured degree of compaction, with a Pearson correlation coefficient of 0.859 and a coefficient of determination R² of 0.738, indicating that the Z-direction peak acceleration has potential as an indicator for evaluating compaction quality. Meanwhile, the vibration energy of the subgrade exhibited a non-uniform spatial distribution, reflecting the effects of the rolling path, wheel-track position, and fill-material heterogeneity on energy propagation. The findings provide experimental references for understanding the dynamic response and energy variation laws of soil-rock mixed-fill subgrade during vibratory compaction.