## 5 Conclusions  
Roadbeds built on soft clay foundations often experience significant post-construction settlement under traffic loads. To analyze this phenomenon, this study conducted numerical simulations to investigate the vibration response of different roadbed-foundation systems under vibration loads and analyzed the propagation characteristics of the vibration waves in these systems. Vibration reconsolidation tests were conducted to study the reconsolidation behavior of soft clays under vibration loads after initial consolidation under static loads. From the perspectives of both wave propagation and vibration, this research analyzed the reasons for the large post-construction settlement of roadbed-soft clay foundation systems under traffic vibration loads. The main findings are as follows:  
1. In the roadbed-soft clay foundation systems, the kinetic energy generated by traffic vibration loads primarily propagates in the vertical direction, transferring energy to the soft clay layer beneath the roadbed, with minimal propagation outward in the horizontal direction. The predominant vibration within the entire system is mainly concentrated in the roadbed and the underlying soft clay layer near the vibration source;
2. The vibration reconsolidation phenomenon of soft clays is very significant. The equivalent static load increment of the vibration load is related to the frequency and amplitude of the vibration load, as well as the static load on the soil;
3. The consolidation process and mechanism of soft clays under vibration loads differ significantly from those under static loads. The consolidation process under a vibration load involves two parts: the decrease in effective stress due to the structural damage caused by vibration and the increase in effective stress due to compression hardening of the soil skeleton;
4. In engineering practice, the distribution of vibration loads in the foundation under traffic loads could be obtained through wave propagation analysis first. Combined with the results of vibration reconsolidation tests of the soft clay, the total post-construction settlement of the roadbed-soft clay foundation system under the traffic vibration loads could be estimated using the layer-summation method. The vibration reconsolidation test proposed in this paper is based on a new research idea that focuses on the equilibrium state reached by the soil under vibration load. Based on this idea, many experimental studies can be carried out. However, the experimental research in this paper has some limitations. First, limited by experimental conditions, it is currently impossible to obtain reliable settlement-time and pore water pressure-time relationships, both of which are crucial for understanding the vibration consolidation process and the physical mechanisms behind it. Moreover, the experimental conditions in this study are relatively simple, and the potential influence of factors such as soil type (in-situ soil, remolded soil), initial soil state (consolidation pressure, overconsolidation ratio), and the nature of the vibration load (frequency, amplitude, and waveform) on the experimental results has not been fully considered. This limits the scope of application of the experimental results. Future studies with more precise experiments are needed to achieve a more comprehensive understanding of the vibration consolidation process. The vibration reconsolidation test of soft clay is a new idea for studying the response characteristics of soft clay under vibration load under drained conditions, and it is still in the exploratory stage. This test can also be used to study the application of vibration load in the fields of foundation treatment, sludge solidification, etc., and is expected to become a new hot spot in future experimental research. **Author Contributions:** Conceptualization, T.X. ; methodology, F.X. ; software, F.X. and Z.W. ; formal analysis, F.X. ; investigation, F.X. ; data curation, Z.W. ; writing--original draft preparation, F.X. and Z.W. ; writing--review and editing, T.X.