## 3 Experimental Results
### Variation of Undrained Shear Strength with Cone Penetration and Water Content  
Many researchers performed trials to estimate the shear strength of soils with the parameters derived from consistency testing. Studies from the literature also show that the ratio of undrained shear strength at the plastic limit to that at the liquid limit also shows a wide variation. For example, [PERSON] and [PERSON] [52], [PERSON] and [PERSON] [53], and [PERSON] and [PERSON] [35] showed that the ratio was 100. On the other hand, [PERSON] [54] proved that the ratio of shear strength at the plastic limit to that at the liquid limit depends on the activity of the existing clay mineral. For example, this ratio is around 100 for montmorillonite mixtures, but around 30 for kaolinite mixtures. In this study, the changes in undrained shear strength together with water content and cone penetration were obtained for _NaM-CaM_, _NaM-K_ and _NaM-S_ mixtures. In Figure 4a, in the solid state of the soil, the water contents vary between 15.06% and 38.33%, while the cone penetration depths are between 39.07 mm and 30.99 mm. In this case, the undrained shear strengths were obtained as less than 1 kPa. In the _NaM-CaM_ mixtures, the cone penetration depth continued to decrease with the increasing water content, and the undrained shear strength values in this situation continued to increase. For example, for _NaM-CaM_ mixtures, the cone penetration depth was 1.97 mm, the water content was 65.83% and the corresponding undrained shear strength was 171.88 kPa (Figure 4a). Then, with the increasing water content, the cone penetration depth also increased, and the corresponding undrained shear strength values decreased. After the cone penetration depth exceeded 20 mm (liquid state), the water contents varied between 288.23% and 488.86% (Figure 4a). Undrained shear strength values decreased to lower than 1 kPa in the liquid state, similar to that in the solid state. Compared to _NaM-CaM_ mixtures, both _NaM-K_ and _NaM-S_ mixtures showed a closer behavior to each other. One of the main reasons for this is that in _NaM-CaM_ mixtures, the differences in water content for 11 mixtures were very small depending on the mineralogical properties of the mixtures. Compared to _NaM-CaM_ mixtures, _NaM-K_ and _NaM-S_ mixtures, which have lower plasticity, showed a wide scattering due to the wide range of variation in water content. For example, in _NaM-K_ mixtures during the experiments, the water content for 100% _NaM_ varied between 10.38% and 454.28%, while in the case of 100% \(K\), the water content was between 11.41% and 89.72%. This difference shows that the water requirements required for the mixtures to reach the liquid state vary depending on the mineralogical properties of the clay blends. Figure 3: Relationship between cone penetration and water content for (**a**) _NaM–CaM_ mixtures, (**b**) _NaM–K_ mixtures and (**c**) _NaM–S_ mixtures. As shown in Figure 4b, the highest undrained shear strengths obtained were 171.88 kPa and 30.33 kPa for 100% _NaM_ and 100% \(K\) at 65.83% and 38.67% water contents, respectively. In Figure 4c, the test results for very high-plasticity _NaM_ and low-plasticity \(S\) mixtures are shown. In the solid state, although both _NaM_ and \(S\) clays have low water content, high cone penetration depth and low undrained shear strength, their consistency changed with increasing water content and exhibited different behaviors depending on the mineralogical properties of _NaM_ and \(S\). The highest undrained shear strength values for 100% _NaM_ and 100% \(S\) were 171.88 kPa and 9.28 kPa at 65.83% and 31.65% water contents with 1.97 mm and 8.48 mm cone penetrations, respectively (Figure 4c). While there was a limited decrease in the water-absorption capacity of _NaM_-_CaM_ mixtures with increasing _CaM_ content, the water-absorption capacity of the mixtures decreased significantly with increasing \(K\) and \(S\) contents. For this reason, the water content values of the mixtures in Figure 4b,c show a scattered behavior.