## 3 Experimental Results  
### Variation of Cone Penetration with Water Content  
In this study, to determine the liquid limit of the clay-clay mixtures, the standard British cone [25] was used (80 g, 30\({}^{\circ}\)). Fall cone test methods were used as a more advantageous method as they allow the determination of liquid and plastic limits at the same time. The use of power law functions to describe the variation of water content (\(w\)) with \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Minerals** & _NaM_ & _CaM (\%)_ & _K (\%)_ & \(S\) \\ \hline SiO\({}_{2}\) & 83 & 72.2 & 50.7 & 47 \\ Al\({}_{2}\)O\({}_{3}\) & 5.5 & 14 & 34 & 36 \\ Fe\({}_{2}\)O\({}_{3}\) & 0.2 & 0.7 & 0.6 & 0.6 \\ TiO\({}_{2}\) & 0.05 & 0.05 & 0.8 & 0.8 \\ CaO & 0.4 & 1.1 & 0.6 & 0.6 \\ MgO & 2.10 & 3.2 & 0 & 1.4 \\ Na\({}_{2}\)O & 0.15 & 0.25 & 0 & 0 \\ K\({}_{2}\)O & 0.6 & 1 & 0 & 0 \\ SO\({}_{3}\) & 0 & 0 & 0.3 & 0.6 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Chemical analysis of _NaM_, _CaM_, \(K\) and \(S\) clays. Figure 2: SEM images of (**a**) Na-Montmorillonite (_NaM_), (**b**) Ca-Montmorillonite (_CaM_), (**c**) Kaolinite (_K_) and (**d**) Sepiolite (_S_). cone depth (\(d\)) relative to more traditional semi-logarithmic formulations was proposed by [PERSON] [43; 44]. In this case, the relationship between cone penetration and water content can be written as in Equation (6):  
\[w=C_{0}\times d^{\beta} \tag{6}\]  
where, \(C_{0}\) is the water content intercept at \(d\) = 1 mm, and \(\beta\) is the slope of the best-fit straight line, respectively. The Fall cone liquid limit \(LL_{FC}\) and Fall cone plastic limit \(PL_{FC}\) in the BS cone were obtained from Equation (6) as the water content on the flow line corresponding to \(d_{LL}\) = 20 mm and \(d_{PL}\) = 2 mm, respectively. Therefore, the Fall cone liquid limit and plastic limit are defined in Equations (7) and (8) ([PERSON], 2000):  
\[LL_{FC}=C_{0}\times(20)^{\beta} \tag{7}\]  
\[PL_{FC}=C_{0}\times(2)^{\beta} \tag{8}\]  
Many studies also focused on the relationship between cone penetration and water content. For more than twenty years, Fall cone tests were frequently used to determine not only the liquid limit but also the plastic limit of cohesive soils [6; 45; 46; 47; 33; 41; 43]. Under these circumstances, it is clear that a constant cone penetration value cannot be obtained at different water contents for natural soils, clay-sand mixtures, sand-clay mixtures, sandy soils or clayey soils. If the water-holding capacity of soils in different states of consistency is defined as Afterberg limits, the assumption that different soils with different liquid and plastic limit values will have unique cone penetration values will not be true [45; 46; 47; 3; 48; 49; 50; 51]. In Figure 3a-c, the relationship between cone penetration and water content of _NaM-CaM_, _NaM-K_ and _NaM-S_ mixtures was obtained, respectively. The mixtures in the experiments started with very small water content values, and the incremental steps were chosen to be small to obtain a cone penetration-water content relationship supported by a huge number of experimental data. Initially, the amount of cone penetration was measured as 40 mm when the mixtures were fully dry, and the soil remained in a solid state since there was no volume change up to a certain point with the increasing water content. In this case, the amount of cone penetration was very low. As the water content continued to increase throughout the experiment, the amount of cone penetration decreased. In this case, the consistency of the soil became a semisolid state. As can be seen in Figure 3a-c, the cone penetration decreased abruptly in the semisolid state. Here, the water content corresponding to the 2 mm cone penetration amount corresponds to the plastic limit values of the mixtures. Afterwards, while the water content continued to increase, the amount of cone penetration also increased. In this range of water contents, the mixtures were at a plastic state.