# Electromechanical Behavior of Afyonkarahisar Clay Under Varying Stress and Moisture Conditions
## 3 Test Results and Discussions
### Sensitivity Assessment  
The maximum range of soil sensitivity can be estimated as follows:  
\[S_{t}=c_{u,max}/c_{u,min}, \tag{10}\]  
This result (\(\mathrm{S_{t}}\approx 1200/120=10\)) indicates that the clay exhibits a sensitivity of approximately 10, which classifies it as a highly sensitive material. Such behavior is characteristic of montmorillonite clays or quick clay-type soils, where even slight disturbances or increases in moisture content can cause a significant reduction in shear strength. In practice, this means that the soil, when dry, may present a misleadingly high bearing capacity. However, even a small change in moisture content can lead to a substantial loss of strength. This reflects the high sensitivity of the studied clay, quantified by a sensitivity index of approximately \(\text{St}\approx 10\), indicating that the undrained shear strength decreases sharply with minor increases in moisture content. Such behavior is characteristic of high plasticity clays (CH), especially montmorillonite and quick clays, where small moisture variations weaken particle bonding and disrupt soil structure. As the pore water content increases, the resulting rise in pore water pressure reduces the effective stress in the soil--a key factor controlling its mechanical performance. This reduction directly leads to lower shear resistance and bearing capacity, making the soil vulnerable to settlement, swelling, and slope instability. Therefore, strict control of drainage and hydrological conditions is crucial to ensure the long-term stability and reliability of structures built on or within such soil. Figure 8 illustrates the correlation between undrained shear strength (\(\text{c}_{\text{u}}\)) and electrical conductivity. The observed relationship is clearly nonlinear, indicating that changes in electrical conductivity do not correspond to proportional changes in shear strength. Instead, the correlation suggests a more complex interaction, where shear strength decreases more rapidly at higher conductivity levels, particularly in the moisture range approaching saturation. This nonlinear trend may be attributed to the increase in pore water content, which raises electrical conductivity due to enhanced ion mobility. As saturation is approached, pore water pressure increases, leading to a significant reduction in effective stress. Both effects contribute to the observed decrease in undrained shear strength and reflect the complex interaction between moisture content, pore pressure, and soil structure. The curve (see Equation (11)) implies that electrical conductivity can serve as an indirect indicator of shear strength, but only when its nonlinearity is properly accounted for through empirical or calibrated models. \[\text{c}_{\text{u}}=-114,000\text{ EC}^{2}+7200\text{ EC}+371.25, \tag{11}\]  
Figure 7: Shear strength decreases as a function of increasing relative water content, using Equations (7) and (9). Figure 9 illustrates the reduction in undrained shear strength (\(c_{u}\)) as a function of relative water content (\(w/w_{L}\)). The data clearly show that as the relative water content increases, the shear strength of the clay decreases significantly. This trend reflects the progressive weakening of the soil structure due to higher moisture levels, which reduce interparticle bonding and effective stress. The decline is nonlinear, with a particularly steep drop observed as the relative water content approaches or exceeds the plastic limit. This behavior highlights the sensitivity of high-plasticity clay to moisture changes and underscores the importance of monitoring water content in assessing the mechanical stability of such soils. The curve (see Equation (12)) presented in Figure 9 emphasizes the critical threshold beyond which the soil loses a substantial portion of its shear resistance.