# Study on the Influence of Groundwater Variation on the Bearing Capacity of Sandy Shallow Foundation
## 2 Experimental Tests
### Simulation Plan  
For the simplification of the problem in Section 3.1, two influencing factors of water-level fluctuation range and water-level fluctuation form are added in the numerical simulation. The water-level fluctuation range refers to the thickness of Zone B in Section 3.1. The water-level distribution form contains the horizontal type, the simple harmonic type and the random function type. The specific simulated working conditions are shown in Table 3.  
The water-level fluctuation form is shown in Figure 7. A straight line indicates no fluctuation in the water table. Sine waves represent fluctuations in water levels that are sinusoidal over time. The random function is a uniform distribution function. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Number** & **Factors** & **Elevation of Water** & **Water-Level** & **Water-Level** \\  & **Level** & **Fluctuation Range** & **Fluctuation Form** \\  & **(mm)** & **(mm)** & **Fluctuation Form** \\ \hline
1 & 50 & 10 & sine wave \\
2 & 50 & 20 & sine wave \\
3 & 50 & 30 & sine wave \\
4 & 50 & 40 & sine wave \\
5 & 100 & 10 & sine wave \\
6 & 100 & 20 & sine wave \\
7 & 100 &  
As is shown in Figure 8, the stress and deformation of the foundation for the model under different upper loads assume that the water-level-fluctuation curve is sinusoidal. The closer the color is to red, the greater the stress in this region. The closer the color is to blue, the smaller the stress in this region. The vertical deformation in the upper right corner of the model represents the vertical settlement of the foundation soil under load. The stress and deformation of the soil increase under increasing upper loads, and the effect of the water-level fluctuation is also obvious. The foundation's settlement and the foundation's uplift around the loading can be clearly seen. Figure 9 shows the changes in the distribution of the foundation's plastic zone during the increasing upper load. The blue area represents the plastic deformation of the foundation soil. Due to the influence of gravity stress and pore water pressure on the lower part of the foundation, the plastic development degree of the lower part of the foundation is greater than that of the upper part of the foundation. It is obvious that the plastic zone develops continuously with the increasing upper load until it reaches the ultimate load. Figure 10 is the control chart of the test results and numerical simulation results under different water-level heights. The average error of the experiment and simulation results is less than 8%. The error is within the acceptable range. The error is generated for the following reasons:  
1. During the test, the water content of the soil layer above the water table increased due to the capillary phenomenon of the soil, which led to a decrease in the parameters of internal friction angle and cohesion and a decrease in the bearing capacity. The numerical simulation assumes that the water content of the soil above the water table is the initial water content. Therefore, the bearing capacity of the test result is smaller than that of the simulation result. Figure 8: Variation of foundation stress and deformation with upper load. Figure 7: Schematic diagram of water level fluctuation form: (**a**) straight line, (**b**) sine wave and (**c**) random function. 2. The termination condition of loading during the test is according to the Geotechnical Test Procedure: the deformation of the foundation reaches 1/12 of the width of the loading plate. Then the foundation was considered to be damaged, and the loading was stopped. In contrast, the numerical simulation is loaded until the damage. Therefore, the test may not reach the ultimate bearing capacity of the foundation when the loading is stopped and the p-s curve has not reached the inflection point. Figure 10: Comparison of test and simulation results at different water-level heights: (**a**) initial water level, (**b**) 50 mm water level and (**c**) 100 mm water level.