# Model Tests of Soil Reinforcement Inside the Bucket Foundation with Vacuum Electroosmosis Method
## 3 Results and Discussion
### Effects of Shear Strength and Soil Moisture Content before and after Soil Reinforcement  
Figure 10 shows the photos of the soil change after the soil reinforcement, and Figure 11 shows the undrained shear strength of the soil in T1-T6. \(S_{\text{u}}\)' means the undrained shear strength of the soil before reinforcement, and \(S_{\text{u5}}\), \(S_{\text{u10}}\), and \(S_{\text{u15}}\) indicate the undrained shear strength of the soil at 5 cm, 10 cm, and 15 cm from the wall of the bucket wall after reinforcement, respectively. In T1 and T2, an \(\sim\)2 cm thick crust soil was found under the bucket foundation (Figure 10a). The undrained shear strength of the crust soil was 6-8 kPa, and the water content was approximately 38%. The generation of the crust soil hinders the downward transfer of the negative pressure, restricting any change in shear strength of the soil under the crust. At a depth of 5 cm, the undrained shear strength of the soil is the same as before the reinforcement, and the moisture content of the soil is reduced by 10%. In T2, the electrode increases the vertical negative pressure transmission channel in the soil, and soil reinforcement strength in the horizontal direction is uneven. The undrained shear strength \(S_{\text{u}}\) at 5 cm and 10 cm from the wall of the bucket increased by 1 kPa and 2 kPa, respectively. Figure 10: Photographs showing the soil change inside the bucket foundation: (**a**) Test T1; (**b**) Test T6. Figure 9: Pore pressure, vacuum load versus time: (**a**) Test T1; (**b**) Test T2; (**c**) Test T3; (**d**) Test T4; (**e**) Test T5; (**f**) Test T6. The undrained shear strength of the surface soil is 10 kPa in T3 and T5 and 8 kPa in T4. At a depth of 10 cm in the bucket, the undrained shear strength is 4 kPa in T3 and T5 and approximately 3 kPa in T4. The undrained shear strength of T3 and T5 is about 1.67 times the height of the bucket wall. In T6, the undrained shear strength of the soil is 21.5 kPa, which is approximately 20 times the shear strength before reinforcement, and the reinforcement depth is approximately 4 times of the foundation height. At 10 cm deep, \(S_{\text{u5}}\) and \(S_{\text{u10}}\) of the soil in the bucket are 12 kPa and 18 kPa, respectively, which are 3 times and 4.5 times the corresponding shear strengths in T3. \(S_{\text{u10}}\) is about 3 kPa greater than \(S_{\text{u5}}\). The soil near the cathode has the highest undrained shear strength. After the test, the soil in the bucket is in a hard plastic state and is wrapped tightly around the cathode (Figure 10b). Figure 12 shows the change in moisture content with soil depth, where \(w^{\prime}\), \(w_{5}\), \(w_{10}\), and \(w_{15}\), respectively indicate the moisture content of the soil before reinforcement, at 5 cm, 10 cm, and 15 cm from the bucket wall after reinforcement. The soil has a moisture content of approximately 50% before reinforcement and a moisture content of approximately 55% in the surface soil. In T1-T5, the moisture content at 5 cm deep after soil reinforcement decreases to 40%, and the soil moisture content is about 50% at 20 cm deep, which is the same as soil without reinforcement. Due to the hard soil in the upper part of T6, moisture content was only measured up to 20 cm deep, and the soil moisture content was approximately 38%. Therefore, increasing the driving voltage can effectively decrease moisture content and increase the uniformity of the soil reinforcement in the vertical direction. Figure 11: Undrained shear strength with soil depth for T1–T6: (**a**) Test T1; (**b**) Test T2; (**c**) Test T3; (**d**) Test T4; (**e**) Test T5; (**f**) Test T6. Figure 12: _Cont._  
In this study, the vacuum-electroosmosis reinforcement tests of the bucket foundation under atmospheric conditions were carried out. The vacuum load was the atmospheric pressure difference between the top and bottom top lid, therefore, the maximum vacuum load applied was \(-100\) kPa.