## 3 Field Test Results and Analysis  
### Effect of the Vibration Isolation Trend on Ground Vibration  
Figure 8a,b show the attenuation curves of the peak acceleration and peak velocity in the vertical direction at each test point at the #1 and #2 measurement lines, respectively. No vibration isolation trench was set on survey line #1. The vertical peak value of acceleration and velocity at 8 m away from the tamping point were 338.02 cm/s\({}^{2}\) and 44.68 mm/s, respectively, while they were 138.12 cm/s\({}^{2}\) and 24.15 mm/s at a distance of 12 m. The attenuation amplitude is 59% and 46%, respectively, for the non-vibration isolation trench case. A vibration isolation trench with a length of 16 m, a width of 1 m, and a depth of 1 m is set at 10 m away from the tamping point for survey line 2. The vertical peak value of acceleration and velocity at 8 m from the tamping point were 390.09 cm/s\({}^{2}\) and 51.3 mm/s, respectively, while they were 55.61 cm/s\({}^{2}\) and 12.34 mm/s at a distance of 12 m, which is on the other side of the trench. The attenuation amplitude is 86% and 76%, respectively, for the case with the vibration isolation trench, which achieves an approximately 30% improvement effect. The results indicated that the vibration isolation trench has a significant weakening effect on the vertical vibration caused by dynamic compaction. Figure 8c shows the attenuation curves of the horizontal radial peak acceleration of survey line #1 and line #2, and Figure 8d shows the velocity attenuation curves. No vibration isolation trench was set on survey line #1. The horizontal radial peak value of acceleration and velocity at 8 m away from the tamping point were 238.75 cm/s\({}^{2}\) and 55.63 mm/s, respectively, while they were 105.48 cm/s\({}^{2}\) and 31.41 mm/s at a distance of 12 m. The attenuation amplitude is 56% and 44%, respectively, for the non-vibration isolation trench case. The horizontal radial peak value of acceleration and velocity at 8 m from the tamping point were 290.23 cm/s\({}^{2}\) and 64.29 mm/s, respectively, while they were 81.71 cm/s\({}^{2}\) and 24.60 mm/s at 12 m on line #2. The peak value decreased by 72% and 62% after propagating through the trench. The vibration isolation trench increases the attenuation effect by 16% and 18%, respectively. The above results found that the vibration isolation trench has an obvious isolation effect on the side far from the tamping point in dynamic compaction construction. The closer to the trench, the more obvious the isolation effect is. With the increase in the distance from the trench, the isolation effect of the vibration isolation trench gradually weakens. In this test, when the tamping distance is greater than 25 m, the vibration isolation effect can be almost ignored. Additionally, by comparing the PGA and PGV with and without the vibration isolation trench at 8 m, the vibration wave of the soil in front of the trench is strengthened due to the reflection of the vibration wave, which may cause damage to the trench structure. Figure 7: The size of the isolation trench. The toe of the Yangtze River dike is most affected by the dynamic compaction vibration, with a maximum horizontal radial acceleration of 13.8 cm/s\({}^{2}\) and a velocity of 4.9 mm/s. The vibration effect gradually weakened with the increase in the taming distance and the height of the dike, and the peak acceleration and velocity decrease to the minimum at the dike top. Since the maximum horizontal vibration acceleration of the Yangtze River dike is less than 45 cm/s\({}^{2}\) and the maximum vibration speed is less than 50 mm/s, it can be considered that the impact of dynamic compaction vibration on the Yangtze River dike under 1000 kN\(\cdot\)m compaction energy is within the safe range and will not cause damage to the Yangtze River dike.