###### Abstract  
Dynamic compaction is a widely used method to strengthen the foundation, which can cause significant impacts on surrounding structures, making vibration control measures necessary. This study investigates the effectiveness of isolation trenches in reducing ground vibration caused by dynamic compaction in a typical multi-layered alluvial soil foundation adjacent to the Yangtze River. A combination of field testing and numerical simulation was employed to evaluate the vibration isolation effect of trenches at different depths and locations. The results show that trenches have a significant vibration isolation effect on the side away from the tamping point, but they can have an amplifying effect between the trench and tamping point. The effectiveness of the isolation trenches increases with deeper trenches and distance from the tamping point, but the amplification effect decreases with increasing depth. Therefore, when employing trenches, reinforcement measures must be adopted, and a suitable trench depth should be selected. The closer the isolation trench to the dike, the better the protection will be. The study provides effective guidance for designing isolation trenches in similar dynamic compaction processes, emphasizing the importance of considering spatial attenuation characteristics and selecting appropriate trench depths and locations. dynamic compaction; isolation trenches; spatial attenuation; vibration control; multi-layered alluvial soils 2023  
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Y.Z. vibrations on surrounding areas. Regarding the mechanism of ground improvement and influencing factors, [PERSON] et al. [15] studied the compaction behavior of soil aggregate mixed ground and divided the soil into three zones based on the distribution of stress waves, namely an impact strengthened zone, a plastic stress wave strengthened zone, and an elastic zone in which the strength of the soil is not reinforced. [PERSON] et al. [16] elucidated the mechanism of loose granular soil reinforcement from the particle scale. [PERSON] et al. [17] conducted experiments to investigate the crushing effect of gravel soil during DC and proposed a constitutive model applicable to calculating the behavior of gravel soil. [PERSON] et al. [18] proposed a dynamic fluid-solid coupled finite element method (FEM) combined with the soil cap yield hardening model to analyze the improvement of saturated ground under dynamic compaction. The results showed that lowering the groundwater level was more important than increasing the soil permeability for ground improvement. [PERSON] et al. [19] investigated the effect of groundwater level on DC and found that overall ground improvement was the result of compaction and liquefaction combined densification, with the depth of groundwater controlling the relative contributions of these two mechanisms. [PERSON] et al. [20] studied the compaction process of loess through field tests and numerical simulations and found that the effective improvement depth could be estimated well using the modified Menard formula and that the ramming energy was the most important factor affecting ground compaction. In terms of evaluating the reinforcement performance, [PERSON] et al. [21] developed a method for estimating the deformation performance of granular soil induced by DC by investigating the factors influencing ground deformation. [PERSON] et al. [22] evaluated the reinforcement performance of high energy DC. [PERSON] et al. [23] proposed a scheme for predicting soil behavior after compaction by considering factors such as ramming energy, times, spacing between tamping points, and compaction sequence during multi-point compaction. [PERSON] et al. [24] simulated the DC of a stone-pile yard based on the material point method, established an approximate formula for the effective improvement range of dynamic compaction, and proposed appropriate tamping point spacing through multi-point compaction simulation. [PERSON] et al.