# Bearing Capacity of Shallow Foundations on Unsaturated Silty Soils
## 3 Results and Discussion  
After the soil samples were created for the pressure plate tests and filter paper tests, they were statically compressed, as was carried out for the other tests, and the samples were taken with the help of metal rings with a diameter of 50 mm and a height of 20 mm. The samples were fixed by placing porous stones on the samples in order to reach the SSD and were kept in distilled water for 7 days. The samples taken from the model loading tests, on the other hand, were placed immediately on the filter paper to start the equilibrium stage and the MS values of the prepared samples were measured. The SWCCs of the samples formed at three different void ratios were determined by the pressure plate and filter paper method. In the experimental study, model tests were conducted with soil samples compacted with targeted VRs (0.65, 0.7 and 0.75) and SSDs (i.e., 65%, 70%, 75%, 85%, 100%) considering seasonal groundwater level changes. To reflect this scenario, the samples were statically compressed with targeted VRs at four different SSDs. Since experiments were carried out on samples with three different VRs, the samples were prepared at these VRs for the SWCC experiments. Therefore, SWCC experiments were carried out on three samples (0.65, 0.7 and 0.75 void ratios) and SWCCs have been created according to the GWC. The most ideal curves of the experimental data were created with the [PERSON] (1980) [70] model, which is one of the SWCC generation models available in the literature, for MS values ranges between 0 and 1,000,000 kPa (Figure 5). Since the SWCC data at high MS range could not be determined with the pressure plate (the suction was determined with the pressure plate up to 800 kPa), it was measured by the filter paper method, and it was again found to be compatible with the curves obtained from the [PERSON] (1980) [70] model. The AEVs of the samples with 0.65, 0.70 and 0.75 void ratios have been determined as 12.4, 10.2 and 8.0 kPa, respectively. Figure 5: SWCCs of silly soil prepared at different VRs. Samples with VRs of 0.65, 0.70 and 0.75 and SSDs of 65%, 70%, 75%, 85% and 100% were created using static compression. The samples were saturated under water for 9 days. The SS were recorded as a function of horizontal displacement up to the maximum value. As seen in Figure 6, a clear peak is observed in the stress-strain graphs at each net stress (59, 98 and 147 kPa) at MS values higher than the AEV in the samples with 0.65 VR. No significant peak has been observed for the saturated state. A similar situation is observed for the samples with VRs of 0.70 and 0.75. Figure 6: Shear strain curves for silt sample with VR = 0.65 (from shear box tests): (**a**) SSD = 65%; (**b**) SSD = 70%; (**c**) SSD = 75%; (**d**) SSD = 85%; (**e**) SSD = 100%. Figure 8 shows the failure envelopes formed by considering the maximum SS values of the samples. Table 5 lists the SS parameters of the soils obtained from these failure envelopes. With the increase of the SSD, a decreasing trend is observed in the cohesion values and the SS angles of the samples with three different VRs. In the literature, it is a known behavior that a decrease in the SSD/increase in the MS value will cause an increase in the cohesion value [55]. In addition, the observation that the increase in the MS value causes an increase in the angle of SS is compatible with the data of [PERSON] and [PERSON] (2014) [53]. Figure 9 shows how the SS of silt soils tested at three different VRs varies with both the NNS and the SSD. The results show that the effect of the SSD on the SS decreases as the NNS value increases. In the tests carried out under NNSs of 59 and 98 kPa, there was  
Figure 8: SS-SSD relations under different VR and NNS: (**a**) VR = 0.65; (**b**) VR = 0.70; (**c**) VR = 0.75.