## 3 Results  
In this section, the deformation and internal force development of different pile types at a steady state are investigated by analyzing the results of model test data to examine the horizontal static failure load of the skirt-pile foundation. The primary focus of this study is to examine the horizontal ultimate bearing capacity of the skirt-piles and the force-deformation behavior of the skirt-piles under both horizontal static loading and cyclic loading conditions through horizontal static loading tests. The horizontal static loading system primarily consists of components such as steel wire rope, a \begin{table}
\begin{tabular}{c c c} \hline \hline
**Case NO.** & **Pile Type** & **Test Type** \\ \hline Case 1 & Monopile & Horizontal static load test \\ Case 2 & I & (graded loading, \\ Case 3 & II & 15 N per stage) \\ \hline Case 5 & Monopile & Horizontal cyclic load test \\ Case 6 & I & (loaded displacement \\ Case 7 & II & amplitude A = \(\pm\)5 mm, cycle \\ Case 8 & III & number N = 4500) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Test case on the model pile. Figure 4: Diagram of the sensor arrangement. fixed pulley, weights, a weight plate, a steel frame, and other structures, and the details of the loading device can be observed in Figure 5. The testing system connects the weight plate with the model pile through the fixed pulley using the wire rope. During the loading process, the system gradually places weights on the weight plate, thus converting the vertical self-weight of the system into a horizontal load applied on the pile. It is important to note that friction between the wire rope and the fixed pulley is ignored during the loading process. By conducting these tests, the force deformation law of the skirt-pile can be determined under different loading conditions. The horizontal static force was applied to the pile foundation by the slow maintenance load method, and a constant step loading increment of 15 N was adopted. The horizontal static force test curves of different sizes of skirt-piles and monopiles were obtained. Figures 6 and 7 present the outcomes of the static testing, with the load-deflection curves showcased in Figure 6. It is evident that the inflection point of the load-displacement curve is not apparent for skirt-piles I, II, and III. Thus, the criterion put out by [PERSON] [39] is used to assess the piles' ultimate horizontal bearing capability, which assumes that the ultimate state of the small-diameter driven pile occurs at 20% of the pile diameter. The load equal to the displacement at 0.2 d (10 mm) in the figure can be used to determine the pile's ultimate bearing capacity. The horizontal ultimate bearing capacities of the monopile and skirt-piles I, II, and III in pack and clay are 118 N, 134 N, 143 N, and 174 N, respectively. Evidently, the skirt-pile foundations exhibit a higher horizontal ultimate bearing capacity compared to the monopile foundation, and the three skirt-piles increased the horizontal ultimate bearing capacity by 13.6%, 21.2%, and 47.5% compared to the monopile foundation. This can be attributed to the added skirt acting like a barrel foundation, which can limit the horizontal displacement to a great extent. Furthermore, increasing the diameter of the skirt enhances the load-bearing performance of the foundation more effectively than deepening the skirt. Figure 7 presents the bending moments of the different pile types under various loading conditions. The following image shows that the model pile's damage mode is near the development of plastic hinges; as a result, the model pile may be described as flexible. Figure 5: Horizontal static loading device. The bending moment increases proportionally with the amplitude of the applied horizontal load. The skirt effectively redistributes the applied loads, leading to changes in the distribution of the bending moment along the length of the pile. Notably, the maximum bending moment of the monopile is observed at a depth of 30 cm below the soil surface.