# Study on Shielding Effect of the Pile Group in a Soft-Soil Foundation
## 3 Results
### Stress Analysis  
The displacement field provides a visual representation of the disturbance effects caused by the pile group, whereas the analysis of soil stress field is essential for elucidating the mechanism of piling disturbance [40]. Particularly, the distribution of maximum principal stress can reflect the soil's strength, stress transmission, and deformation characteristics [41]. Figure 9 depicts the maximum principal stress distribution of soil at a depth of 5 m. For a newly installed row of piles (Figure 9a), there is a connected zone of stress increase in the Y direction between piles. As subsequent piles are installed, this high-stress connected zone extends in the X direction (Figure 9b,c), with the stress between piles in the same row decreasing. The results suggest the redistribution of soil stress after piling in order. Figure 8: Lateral displacements induced by soil squeezing in the E and W directions at the ground surface. Figure 9: Distribution of the maximum principal stress in the soil profile at a depth of 5 m; (**a–c**) the maximum principal stress contour maps of the soil after the installation of the first row, second row, and third row piles, respectively. To comprehend the redistribution pattern of soil stress surrounding the piles, radial stress values, quantitatively equal to the maximum principal stress, of the soil grids in the outermost ring of the pile body were extracted. Figure 10 presents the radial stresses of the soil grids around piles (P1-P9) after the consecutive installation of three pile rows. When a pile row is just finished, the radial stress distribution around the piles is uniform in all directions. With the penetration of new piles, the original stress ring is deflected, and a stress-increasing zone is formed along the W-E direction (disturbance direction), meantime the stress increases along the N-E direction and S_E direction. The former indicates that the stress on the front side of the pile is exerted by soil compressions, while the latter indicates that the local soil around is inclined to form a stress concentration area, and both of them may contribute to shielding the soil behind the pile. Furthermore, to quantitatively characterize the stress distribution, the X-direction stress values of soil along the depth were extracted at a distance of 5 m from the P5 center in both the W and E directions (Figure 11). This showed that in the initial state, the X-direction stress of soil increases linearly with depth, while as the three rows of piles are installed, there is a distinct inflection that appears at the bottom of the piles (depth = 15 m), where soil stress significantly increases. This implies that the existing piles, of which the length was 15 m, had a certain shielding effect on soil disturbance. Moreover, the superposition effect of soil stress was observed in both the W and E directions during the sequential installation of the three pile rows. Following the installation of the first row of piles, a larger stress increment was caused in the W direction, and the shielding effect of the existing piles reduced the disturbance of the soil mass, which was manifested by the extremely small stress increase caused by the penetration of the second and the third rows of piles. For the E-direction soil (Figure 11b), as the piles approached row by row, the stress superposition effect of the soil gradually increased, and the third row of piles caused a significant stress increase in the soil. Figure 10: Distribution of radial stress in soil around the piles at the ground surface. Figure 12 demonstrates the variation of soil stress-XX for the A-A' profile at a depth of 5 m. Following pile penetration, the X-directional stress of soil near the pile increases sharply. As the horizontal distance from the P5 center increases, the stress significantly decreases.