# Study on Disturbance Mechanism of Squeezed and Non-Squeezed Soil Piles on Soft Soil Foundation
## 5 Discussion  
Three important indicators--namely, horizontal displacement, vertical displacement, and horizontal stress--were selected to compare and analyze the disturbance effects on the soil of three types of piles: hydrostatic piles, bag grouting piles, and bored piles (Figure 29). Regarding horizontal displacement, it is evident that hydrostatic piles cause the greatest disturbance during the pile driving process, followed by bag grouting piles and bored piles. The horizontal expansion of the pile during the pile driving process may be the controlling factor that affects the magnitude of disturbance effects, with hydrostatic pile requiring a nearly zero aperture to be expanded to 500 mm during the piling process, bag grouting pile usually expanding the aperture from 300 mm to 400 mm, and the bored pile not expanding the aperture. In addition, the disturbance of soil horizontal displacement caused by the three types of piles is inversely proportional to the distance between the soil and the pile center. The same conclusion applies to vertical displacement. It is worth noting that the horizontal disturbance of the three types of piles on the soil during the pile driving process is greater than the vertical disturbance. Therefore, a further study on the disturbance characteristics of the horizontal stress field was conducted, and a general rule was obtained that soil stress increases as the horizontal distance from the pile center decreases. Furthermore, the stress changes produced by hydrostatic piles during the pile driving process are the greatest, followed by bag grouting piles and bored piles. These findings provide an important reference for selecting pile foundations. According to the previously mentioned research, the penetration of piles causes the most disturbance to the soil in the horizontal direction. Therefore, under the same soft soil parameters and pile length conditions, 0.1 kPa and 1.0 mm were chosen as the characteristic values of horizontal stress and horizontal displacement, respectively, to visually represent the horizontal disturbance range of the three types of piles on the soil. By standardizing and comparing them, more precise conclusions were reached. Using 0.1 kPa as the characteristic value of horizontal stress, the horizontal disturbance ranges of the three are, in order, 3.8 m, 2.2 m, and 3.5 m. The normalized values are 7.6, 5.5, and 3.5, respectively, when divided by the pile diameter. The maximal disturbance range is roughly 1/5 of the pile length above the  
Figure 28: Contour map of additional stress and displacement for the bored pile. pile tip. Using 1.0 mm as the characteristic value of horizontal displacement, the horizontal disturbance ranges of the three are 7.6 m, 3.0 m, and 1.1 m, respectively. The normalized values are 15.2, 7.5, and 1.1 when divided by the pile diameter, respectively. The horizontal disturbance range is at its greatest near the surface. Consequently, the hydrostatic pile disturbs the soil the most, followed by the bag grouting pile and the bored pile. It is worth noting that this comparison study by numerical simulation has made some simplifications. For example, for bag grouting piles, the nonlinear process of slurry pressure distribution throughout the hole is not considered, and neither is the expansion degree and sequence of different formation stiffness, which may have affected the calculated results. For the bored piles, it is difficult to use them in soft soil without a steel shield; also, the damage to soft soil structure caused by unloading is not considered. These should be further considered in practical construction. In order to select the best piling method, it is important to consider both the disturbance effect and engineering practice. Based on practical experience, hydrostatic piles have advantages such as low unit-bearing capacity cost, guaranteed quality, short construction time, adjustable pile positions, and low slurry production. However, their construction requires strict bearing capacity requirements for the site.