# Model Test of Dynamic Response of Living Poles Slope Under Train Loads
## 3 Dynamic Response of Living Poles Slope Under the Train Loads
### Dynamic Stress Response of Embankment Slope Under Train Load
#### 3.1.1 Variation Law of Earth Pressure Response Peak with Different Train Loads  
The variation curves of the peak earth pressure at different depths under different excitation frequencies, coaxial loads, and vibration amplitudes are shown in Figure 9. It can be seen from Figure 9a that the earth pressure was gradually improving with the raising of the excitation frequency. It is also noted that the earth pressure of the bed surface layer increased by 5.2% and 7.5%, respectively, during the raising of excitation frequency from 2 Hz to 4 Hz (using 2 Hz data as the reference point), which indicates that the increase of train speed and the rise of excitation frequency will lead to the improvement of earth pressure of the bed surface layer, and with the increase of depth, the sensitivity of earth pressure changes with frequency decreases. The earth pressure decayed rapidly along the depth direction. Taking the 0.14 m data as the reference, the earth pressure at the bottom of the foundation bed decayed by 43.6%, and the earth pressure at the embankment body decayed by 63.5%, 86.9%, and 86.5%, respectively. The slope of the change curve shows that the decay rate of soil pressure is gradually decreasing with the increase of burial depth, showing a trend of first fast and then slow. Another observation was that the depth that was influenced by the train loads was 0.89 m, and the earth pressure had decayed very little beyond 0.89 m. When the buried depth was below 0.89 m, the earth pressure was similar in magnitude, which was less affected by the train loads. The reason for this rule is mainly related to the gravel grading, the thickness of the ballast layer, and the mechanical properties of the embankment filling. The gravel grading meets requirements, and the ballast thickness slightly exceeds specification, and the embankment filling is mainly silty clay, resulting in the test of the embankment slope damping being larger.  
As can be seen from Figure 9b, with the raise of axle load, the earth pressure gradually increases. In the process of the axle load increasing from 12.24 kN to 20.52 kN (taking 12.24 kN data as the reference point), the earth pressure on the surface of the foundation bed improved by 14.5%, 23.8%, and 34.3%, respectively. It is interesting to observe that the increase in train axle load led to the improvement of the soil pressure on the surface layer of the bed. The slope of the change curve shows that the sensitivity of earth pressure with the change of static axial load decreases with the increase of depth. As shown in Figure 9c, with the improvement of vibration amplitude, the earth pressure gradually increases. In the process of the vibration amplitude improving from 11.1 kN to 20.1 kN (taking 11.1 kN data as the reference point), the earth pressure on the surface of the foundation bed increased by 9.7%, 15.1%, and 20.6%, respectively. Increasing the train's vibration amplitude resulted in higher soil pressure on the surface layer of the bed. The slope of the change curve shows that the sensitivity of the soil pressure to the change in vibration amplitude decreases with increasing depth. The greater the vibration frequency is borne by the embankment surface, the higher the axial load and vibration amplitude, and the faster the attenuation speed of earth pressure in the embankment. It is shown in the figure that the larger the earth pressure is, the greater the absolute value of the slope of the attenuation curve is. Another observation was that the increased rate of earth pressure in different axial load conditions was greater than in different vibration amplitude conditions. However, it is interesting to observe that the 2.76 kN of the increase step by step of axle load is less than the 3 kN of the improved step-by-step of vibration amplitude. It shows that the influence of the axial load on the earth pressure of the embankment slope is greater than that of the vibration amplitude.