# 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 Law of Living Poles Under Train Load
#### 3.2.1 Bending Moment of Taproot of Living Poles  
The strain time-history curve of measuring point Z2 on living pole A in working condition 1 is shown in Figure 11.  
There was no additional load on the slope before 400 s, so the curve fluctuation before that time had nothing to do with the train load. In the process of vibration excitation, the train load deformed the slope body, and then the strained the living poles, so the bending moment of the pole body gradually increased. As can be seen from Figure 11, the  
Figure 11: Time curve of strain of Z2 on pole A under working condition 1.  
Figure 10: Displacement distribution of slope under different axial loads.  
fluctuation amplitude of the bending moment of the living poles in the excitation process is the same as that before the excitation. The repeated tension and compression deformation of the living poles cannot be caused because the soil dynamic stress is transmitted to the living poles decays to a smaller value, leading to no significant change in the amplitude of the bending moment.  
The distribution of the peak bending moment of the taproot under different coaxial loads is shown in Figure 12. The measuring point with a buried depth of 25 mm on the living pole B failed to collect data. And the buried depth in Figure 12 refers to the vertical distance between the measuring point and the slope surface.  
As can be seen from Figure 12, the larger the axle load of the train, the larger the bending moment generated by the living poles. This rule is especially obvious at the measuring point with a depth of 9 cm. It may be that when the axle load is larger, the earth pressure transmitted by the soil to the living poles is greater, and then the living poles produce a bigger bending moment. The bending moment generated on the taproot segment between the buried depth of 9 cm and 14 cm gradually decreased to 0 with the increase of the buried depth, while the bending moment generated on the taproot segment between the buried depth of 14 cm and 18 cm gradually enlarged with the increase of the buried depth. As can be seen from Figure 12, the bending moment between the buried depth of 9 cm and 18 cm changes almost linearly. The reason for this rule may be that the deformed soil exerts an X-direction horizontal force on the taproot, under the action of the load, a reverse bending point b was produced. Between the taproot and lateral root, the upper around 2/3 taproot was X side in tension, and approximately 1/3 of the lower  
Figure 12: Peak bending moment of the living poles under different axial loads: (**a**) bending moment of living poles \(A\); (**b**) bending moment of living poles B; (**c**) bending moment of living poles C.  
section was under tension on the opposite side. It is agreed that the bending moment is negative when the taproot is under tension on the X side.  
As the slenderness ratio of the taproot is relatively big, it is a flexible structure, so it is easy to produce many anti-bending points in the process of supporting. The peak bending moment distribution diagrams in Figure 12 all show three inflection points. The position of the inflection point a and c are very close to the lateral roots, probably due to the rigid connection between the lateral roots and the taproots. The forces generated by the deformation of the lateral roots are simplified to stresses and bending moments in different directions at the rigid nodes, and the bending moments at the rigid nodes make the bending moments on the taproots change abruptly, so the taproots have opposite moments above and below the lateral roots. The inflection points shown in Figure 12 do not overlap with the positions of the lateral roots due to the errors in the positions of the monitoring points and the test data.