# Bearing Capacity of Shallow Foundations on Unsaturated Silty Soils
## 3 Results and Discussion
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**e**} & \multirow{2}{*}{**SS Parameters**} & \multicolumn{5}{c}{**SSD, \%**} \\ \cline{3-8}  & & **100** & **85** & **75** & **70** & **65** \\ \hline \multirow{2}{*}{0.65} & c & 5.5 & 29.1 & 32.9 & 38.8 & 45.1 \\  & \(\emptyset\) & 27.4 & 27.8 & 28.3 & 30.8 & 31.5 \\ \hline \multirow{2}{*}{0.70} & c & 7.1 & 31.7 & 39.1 & 38.9 & 45.9 \\  & \(\emptyset\) & 24.2 & 22.6 & 23.8 & 26.9 & 27.6 \\ \hline \multirow{2}{*}{0.75} & c & 9.6 & 30.9 & 35.1 & 36.8 & 41.5 \\  & \(\emptyset\) & 21.1 & 17.8 & 18.8 & 22.4 & 23.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: SS parameters of samples with different SSD. a peak/trough fluctuation between the SSDs of 70% and 75% SSDs. This shows that in addition to the MS of the silty soil sample, a different void structure has the strongest or weakest effect on the SS at a certain SSD [53; 60]. In the current work, model foundations experiments were conducted in a cylindrical tank filled with statically compacted soils to examine the UBC of foundations on unsaturated soils under undrained loading circumstances. The model foundations were loaded  
Figure 9: Saturation-shear stress relationships: (**a**) VR = 0.65; (**c**) VR = 0.70; (**e**) VR = 0.75, Saturation-% shear stress increase relationships: (**b**) VR = 0.65; (**d**) VR = 0.70; (**f**) VR = 0.75.  
relatively quickly (1.15 mm/min) to avoid any changes to the suction value of the sample during the loading process. Square and circular shallow foundation models were loaded up to the peak failure conditions to determine the UBC. The dimensions of the glass fiber reinforced polyester tank used are 310 mm in diameter, height of 250 mm and a thickness of 10.2 mm. Model foundations with the largest foundation width of 50 mm were employed in the study. The dimensions of the model mold were selected large enough (>6D) that stresses on the boundaries of the mold due to the loads applied to the model foundation would have a negligible effect. It was confirmed by the control measurements carried out during the tests that no deformation occurred in the mold (The deformation was checked at three different measurement points on the outer surface of the mold.) during loading. Model foundation loadings were performed by using a triaxial loading frame. The vertical displacements of the model foundations were measured with the deformation gauges, and the loads were measured using a load cell (Figure 10). In both measurements, the data were recorded by taking their values at the predetermined deformations. Tests were terminated until the settlements reached 20 percent of the foundation width. After the UBC tests were performed, two samples were taken from the compacted soils using 50 mm diameter stainless steel thin-walled pipes. A total of 96 UC test were performed on the samples taken. The average values of 12 different scenarios when classified with similar VRs and SSDs are shown in Table 6.  
The model footing test results for both saturated and unsaturated silt sample prepared at the VR of 0.65 are shown in Figure 11. As seen, no clear failure point has been observed \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**SSD, \%**} & **VR = 0.65** & **VR = 0.70** & **VR = 0.75** \\ \cline{2-4}  & \(q_{u}\) **(kPa)** & \(q_{u}\) **(kPa)** & \(q_{u}\) **(kPa)** \\ \hline
65 & 116.05 & 71.88 & 54.31 \\
70 & 94.68 & 65.19 & 37.99 \\
75 & 75.58 & 58.89 & 31.23 \\
85 & 68.2 & 36.57 & 29.31 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Angles showing the slope of the SS increase with respect to the MS.  
Figure 10: Model test setup: (**a**) schematic; (**b**) experimental picture. in the curves. Therefore, the UBC values have been evaluated by intersecting the tangents of the initial and the final linear part of the curves. The state of the soil and punching shear failure after the model footing tests can be observed from Figure 12. In the punching failure described by [PERSON] (1973) [44], which is also valid in the current study:  
1.