## 3 Results and Discussion  
### The Accumulated Deformation of the Pile Group Subjected to Horizontal Cyclic Loading  
It is well-known that the pile group will generate a round-trip overturning motion with the change of the load direction under horizontal cyclic loading, and the mono-piles will rotate around the connection point between the top of the pile and the bearing platform. In addition, the center of the pile group foundation will also experience horizontal displacement. In this section, an investigation will be conducted on the cumulative deformation of a pile group in saturated clay soil under varying amplitudes and periods. Figure 8 shows the variations of the displacement of the bearing platform with the number of cycles, and Figure 9 depicts the changes in the rotation angle of the bearing platform with respect to the number of cycles, denoted by N. In this context, \"y\" represents the displacement of the bearing platform, while \"0\" denotes the rotation angle of the bearing platform. Figure 8: The displacement of the bearing platform with the number of cycles at different pile spacings. (**a**) Pile spacing is set at 3 times the pile diameter. (**b**) Pile spacing is set at 4 times the pile diameter. (**c**) Pile spacing is set at 5 times the pile diameter. As illustrated in Figure 8, when the amplitude of horizontal cyclic loading was small (CLR \(\leq\) 0.5), the variations of the horizontal deformation at the bearing platform with the number of cycles were roughly in two stages: (1) the deformation development stage and (2) the deformation stabilization stage. During the first 1000 loading cycles, the horizontal deformation of the bearing platform was in the growth stage. It can be observed from Figure 8 that at the early stage of loading, the horizontal deformation of the bearing platform rapidly increased, and the deformation of the pile group continuously increased with the increase of cycles. After a period of loading, the horizontal deformation of the bearing platform slowly grew, and the growth rate of deformation gradually slowed down compared with the early loading. After undergoing 1000 loading cycles, the horizontal deformation of the bearing platform stabilized and ceased to increase. However, when the amplitude of the horizontal cyclic loading was higher (CLR \(=\) 0.75), the horizontal deformation of the bearing platform exhibited a sharp increase during the initial 1000 cycles, and still increased in the subsequent cycles. Although there was no stable trend in the curve, the growth rate was significantly slower than that in the first 1000 cycles. Meanwhile, the cyclic loading amplitude and pile spacing also have a large influence on the horizontal deformation of the bearing platform. When the pile spacing was set at 3 times the pile diameter, the horizontal deformation of the bearing platform was 3.4 mm, 7.6 mm, and 11.6 mm at 1000 cycles, with the increase of the loading amplitude. When \(\text{CLR}=0.75\), the horizontal deformation of the bearing platform increased by 52.6%, compared with \(\text{CLR}=0.5\), and when \(\text{CLR}=0.5\), the horizontal deformation of the bearing platform increased by 123.5%, compared with \(\text{CLR}=0.25\). The above conditions indicate that the horizontal deformation of the bearing platform increases with the increase of the cyclic load amplitude. In addition, when \(\text{CLR}=0.25\), the horizontal deformation of the bearing platform at 1000 cycles was observed to be 2 mm and 1.4 mm for pile spacings set at 4 times and 5 times the pile diameter, respectively. This represents a decrease of 41.2% and 58.8% compared to the pile spacing set at 3 times the pile diameter. These findings suggest that the horizontal deformation of the bearing platform diminishes as the pile spacing increases under similar force conditions. As shown in Figure 9, when \(\text{CLR}\leq\) 0.5, the angle of the bearing platform rapidly increased at the beginning of loading, and then the growth rate slowed down and finally tended to level off.