# Static and Dynamic Response of Micropiles Used for Reinforcing Slopes
## 3 Results
### Earth Pressure Response Analysis  
In order to study the response of earth pressure on the front and back of each row of the piles, piles #2, #6 and #11 were selected for analysis. The side facing the slope top was defined as the back of the pile, and the other side was defined as the front of the pile. Moreover, the \"share ratio\" is defined as the group effect reduction parameter for decreasing the load capacity of the pile. Figure 12 shows the distribution curve of the earth pressure before and after each row of piles in the static model test. The earth pressure distribution before and after each row of piles is distributed triangularly, that is, the triangular shape is mainly due to the limited number of strain gauges. The earth pressure behind the piles is mainly distributed in the loaded section above the sliding surface, and gradually increases as the load increases. Nevertheless, the soil pressure behind the piles in the embedded section below the sliding surface is relatively minor. The stresses are primarily manifested in the resistance of the soil before the pile and are due to the deformation of the pile body, which also increases with the accumulation of the load. It is worth noting that at 26 kPa, the maximum earth pressure behind the back row of piles is about 87.6 kPa, while that of the middle row of piles is around 68.1 kPa, and that of the front row of piles is roughly 49.5 kPa. Thus, the load on the rear row of piles is the largest, followed by the middle row of piles, and the front row of piles is the smallest. This is consistent with the experimental results. This is because the landslide thrust directly acts on the back row of piles, and the pile body has a blocking effect for the landslide thrust. The load transmitted to the middle and the front row will gradually decrease. It can be seen from the Table 4 that the proportion of piles carried by the rear piles increases initially and then decreases as the load increases with the maximum value (0.411) achieved at 22 kPa. At this time, the ratio of the earth pressure behind each row of piles is back row piles: middle row piles: front row piles = 0.411: 0.348: 0.241. With the further increase in the load, the overall proportion of the middle row piles and the front row piles is slightly larger than under a 22 kPa load. This reveals that the back-row piles are already too deformed, and as such, their load bearing capacity becomes weaker. Meanwhile, the front row and the middle row piles play an increased role, and the earth pressure triggered by the loading is jointly shared by the front row and the middle row piles. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Loading** & **20 kPa** & **22 kPa** & **24 kPa** & **26 kPa** \\ \hline Back row pile & 0.399 & 0.411 & 0.400 & 0.370 \\ Middle row pile & 0.345 & 0.348 & 0.354 & 0.369 \\ Front row pile & 0.256 & 0.241 & 0.246 & 0.261 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The earth pressure sharing ratio of each row of piles (static model test). Figure 13 shows the distribution curve of the earth pressure before and after each row of piles in the shaking table test. As it can be seen from the figure, the maximum dynamic earth pressure is chiefly distributed on the upper and lower sides of the sliding surface. The earth pressure behind the piles is approximately \"triangular\", which is similar with the results of the static test. However, the dynamic earth pressure distribution in front of the pile is quite different compared to the static test, and obvious regularity does not exist. The reason may be the periodicity of the seismic load. Figure 12: Earth pressure distribution in front of and behind each row of piles in the static model tests.