# Electromechanical Behavior of Afyonkarahisar Clay Under Varying Stress and Moisture Conditions
## 2 Materials and Methods
### Schematic Diagram of Experimental Systems  
The experimental setup used for measuring the electrical resistivity is illustrated in Figure 1. The system consists of two copper plates serving as electrodes, two wooden plates providing insulation, a direct current (DC) power supply with constant voltage output, a data acquisition unit, and the test specimen. The copper and wooden plates were placed on the top and bottom surfaces of the clay specimen, respectively, and the assembly was fixed within a uniaxial compression testing machine.  
A constant voltage of 60 V was applied to the system using the DC power source, with the positive and negative terminals connected to separate copper electrodes, thereby completing the circuit. During the uniaxial compression test, voltage values across a 10 \(\Omega\) resistor were recorded at one-second intervals using the data acquisition system. The recorded voltage values were divided by the 10 \(\Omega\) resistance to determine the current passing through the clay specimen.  
\begin{table}
\begin{tabular}{c c} \hline
**Property** & **Value** \\ \hline Soil classification & High plasticity clay (CH) \\ Specific gravity (\(\mathrm{G_{s}}\)) & 2.62 \\ Maximum dry density (\(\mathrm{\rho_{d}}\)) & 1.58 g/cm\({}^{3}\) \\ Optimum water content (w\({}_{\mathrm{opt}}\)) & 21.9\% \\ Liquid limit (w\({}_{\mathrm{L}}\)) & 48.6\% \\ Plastic limit (w\({}_{\mathrm{P}}\)) & 23.0\% \\ Plasticity index (PI) & 25.6\% \\ Shrinkage limit & 5.8\% \\ Moisture content (w) & 10\%, 20\%, 30\% \\ Bulk density \(\mathrm{\rho(w)}\) & 1.738, 1.896, 2.054 g/cm\({}^{3}\) \\ \hline \end{tabular}
\end{table}
Table 1: Geomechanical properties of Afyonkarahisar Clay samples.  
Figure 1: The testing machine and resistivity measurement.  
Using Equation (2), the resistance (R) of the clay sample was calculated by taking the ratio of the fixed voltage (60 V) to the measured current (I). Subsequently, the electrical resistivity (\(\rho_{s}\)) of the clay specimen was determined using Equation (3).  
Furthermore, throughout the uniaxial compression test, the change in electrical resistivity (\(\rho_{s}\)) of the clay sample was monitored in real time, and the temporal variation in resistivity was recorded at one-second intervals by the data acquisition system. The resulting data were then used to plot the resistivity change over time.  
Finally, the electrical conductivity (EC) of the clay specimen was calculated using Equation (4).  
\[\mathrm{R}=\frac{V}{I}, \tag{2}\]  
\[\rho_{s}=Rx\frac{A}{L}, \tag{3}\]  
\[EC=\frac{1}{\rho_{s}}, \tag{4}\]  
In the equations, (I) represents the electrical current flowing through the circuit (A); V denotes the potential difference between the electrodes (V); \(R\) is the measured electrical resistance of clay sample (\(\Omega\)); \(\rho\) represents the electrical resistivity of clay sample (\(\Omega\)-cm); \(L\) denotes the distance between the copper electrodes (cm); and \(A\) refers to the cross-sectional area of the clay sample (cm\({}^{2}\)). To determine the electrode spacing, the specimen height was measured at three different points, and the average value was taken as \(L\). A deformation gauge was used to monitor the changes in specimen height during testing. Simultaneous measurements of load and electrical conductivity were recorded at regular time intervals, and this process continued until the clay specimen failed under uniaxial compression.  
Figure 2 presents a schematic diagram of the experimental setup illustrating the interaction between mechanical loading and electrical resistance measurements. The configuration enables the simultaneous acquisition of electrical resistance data during mechanical loading, thereby allowing for a comprehensive analysis of the relationship between the mechanical and electrical behavior of the clay specimen.  
Figure 2: Schematic diagram of experimental systems for electrical resistance of soil under uniaxial compression.