## 3 Experimental Results
### Variation of Undrained Shear Strength with Liquidity Index and Water Content  
Figure 5 shows the \(3D\) relationship between undrained shear strength, liquidity index and water content for _NaM-CaM_, _NaM-K_ and _NaM-S_ mixtures, respectively. It can be seen from Figure 5(a) that the _NaM-CaM_ mixtures show a wider range of distribution compared to the _NaM-K_ and _NaM-S_ mixtures. As can be seen in Equation (4), when the natural water content is equal to the plastic and liquid limits, \(LI\) becomes equal to 0 and 1, respectively. Figure 5 also shows the \(LL\) and \(PL\) boundaries for all three mixtures. It can easily be inferred that, in _NaM-CaM_ mixtures with very high plasticity, the \(LI\) was less than 0; however, a similar behavior was not observed in _NaM-K_ and _NaM-S_ blends, which have a much lower plasticity. Figure 4: Relationship between cone penetration, water content and undrained shear strength for (**a**) _NaM–CaM_, (**b**) _NaM–K_ and (**c**) _NaM–S_ mixtures. Figure 5: _Cont._Since there is a well-known relationship between the undrained shear strength and the liquidity index of clays, many equations were proposed by past researchers using different regional characteristics and clay mineral types [22, 34, 39, 41, 51, 55]. Therefore, Figure 5a-c reveal that a unique relationship does not exist, at least for fine-grained soils. In Figure 5c, the correlation between \(S_{u}\) and \(LI\) is shown for _NaM-S_ mixtures. The data follow a more uniform path with respect to Figure 5a. In the _NaM-CaM_ mixtures in Figure 5a, low undrained shear strength values were initially obtained at low water contents (0-70%), and the corresponding liquidity index values varied between \(-0.5\) and \(0\). In the experiments, both the undrained shear strength and \(LI\) values increased with increasing water contents. In the 100% _NaM_ sample, the highest undrained shear strength was 171.89 kPa for a water content of 56.62% and a liquidity index of \(-0.10\), while the highest undrained shear strength was 126.10 kPa for a liquidity index of \(-0.09\) at 38.82% water content for 100% _CaM_. After a certain threshold level, the trend of undrained shear strengths was reversed with the increase in the water content of the mixtures. In this case, \(LI\) values also showed a gentle increase. Then, while the water content of the _NaM-CaM_ mixtures increased to between 100% and 400%, the undrained shear strength values decreased considerably (0.1-1 kPa), and the corresponding liquidity index values increased to a range between 1.5 and 2.5. In addition, for 100% _NaM_, 0.5 kPa undrained shear strength and 1.97 \(LI\) were obtained at 430.10% water content,  
Figure 5: Relationship among undrained shear strength, water content and liquidity index for (**a**) emphNaM–_CaM_, (**b**) _NaM–K_ and (**c**) _NaM–S_ mixtures. while 0.46 kPa undrained shear strength and 1.78 _Li_ values were obtained at 226.05% water content in 100% _CaM_ clay (Figure 5a). In Figure 5b, the undrained shear strength, water content and _Li_ relationship of _NaM-K_ mixtures are obtained simultaneously. In this case, mixtures were prepared using \(K\), which has much lower plasticity than _CaM_. In the mixtures obtained by adding 10% \(K\) to 100% _NaM_, the initial _Li_ values varied between \(-\)0.5 and \(-\)1.5. An undrained shear strength of 0.42 kPa and _Li_ value of \(-\)1.36 were obtained at a water content of 11.41% for 100% \(K\). Compared to _NaM-CaM_ mixtures, due to the much lower water-absorption capacity of \(K\), lower water contents were obtained in the _NaM-K_ mixtures. When mixtures were prepared by increasing the \(K\) value by 10% from 100 _NaM_ to 100% \(K\), during the experiment, the water content was up to 430% for 100% _NaM_, while the water content was only up to 89.72% for 100% \(K\).