# Study on Disturbance Mechanism of Squeezed and Non-Squeezed Soil Piles on Soft Soil Foundation
## 2 Materials  
### Numerical Parameters  
Shanghai city, whose high-speed railway lines are the most abundant in China, and whose stratum is characterized as soft soil, is selected as the study area. Before the simulation, selecting appropriate constitutive models to characterize the mechanical behavior of the soil is crucial. The modified Cambridge model is selected as it has been widely used to describe the stress-strain relationship of soft soil due to its few and easy-to-determine parameters [25; 26; 27].  
To obtain the physical and mechanical parameters of the soil, undisturbed soil samples were collected from the study area and then tested. Basic physical parameters, i.e., natural density, natural water content, specific gravity, and water ratio limit were acquired using the ring knife method, drying method (at 107 \({}^{\circ}\)C), pycnometer method, and liquid plastic limit joint measuring instrument, respectively. Triaxial shear tests were performed using the TSY10-1 desktop triaxial equipment, manufactured by Yongchang Science and Education Instrument Manufacturing Co., Ltd. in Jiangsu Province of China to obtain the internal friction angle of the soil. The triaxial shear test sample had a diameter of 3.91 cm and a height of 8 cm. It was saturated employing the vacuum saturation method. The test consolidation confining pressure was set at 100, 200, 300, and 400 kPa, and the shear rate was 0.0064 mm/min. The test was ended when the axial strain reached 20%. The employed triaxial test system (Figure 1a) was controlled by a hydraulic servo controller for confining pressure, and data, such as axial deformation, axial load, drainage volume, and pore pressure, were automatically collected by the computer. Subsequently, the critical failure ratio (see Table 1) of the soil was calculated from the obtained internal friction angle.  
Other two necessary parameters, the compression index and rebound index of the soil, were obtained from K0 consolidation compression unloading tests on soil specimens. In this test, the employed instrument was a GJY type K0 consolidation meter manufactured by Ningxi Soil Instrument Co., Ltd. in Nanjing City of China; the soil samples diameter was  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Parameters**} & **Density** & **Compression** & **Rebound** & **Critical** & **Reference** & **Initial** & **Over** \\  & **(kg/m\({}^{3}\))** & **Index** & **Index** & **Failure Ratio** & **Ratio** & **Porosity** & **Consolidation** \\ \hline Value & 1699 & 0.1192 & 0.0173 & 0.5183 & 0.5183 & 0.7709 & 2.0 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Parameters used in the modified Cambridge model.  
Figure 1: (a) Triaxial test system; (b) K0 consolidation meter.  
6.18 cm and the height was 4 cm. The soil samples were saturated by the vacuum saturation method and tested using a lateral pressure gauge, as shown in Figure 1b. Then vertical loads of 12.5, 25, 50, 100, 200, 300, 400, 300, 200, 100, 50, 25, 12.5, and 0 kPa, respectively, were sequentially applied to the soil. The duration of each load level was controlled at a rate of vertical deformation not less than 0.01 mm per hour. Lateral pressure was provided by water pressure in the closed compression chamber. The vertical deformation was then measured using displacement sensors. Therefore, all parameters for the modified Cambridge model have been acquired, as listed in Table 1.