## 3 Experimental Results  
### Water Retention Curve  
As experienced by [PERSON] et al. [13], good and reliable results can be found by joining data from WP4C and HYPROP. This can be done if osmotic suction is considered negligible because WP4C measures total suction (matric plus osmotic) and HYPROP measures only matric suction. The complete drying branch of the WRC is presented in Figure 3a for the sample simulated in this paper. Similar curves were found for the other samples tested.  
The HYPROP values are presented through continuous lines because data are recorded in a transient mode, while the tensiometers continuously adjust to changing boundary conditions (continuous drying from the top). The different readings of the two piezometers seen in Figure 3a result from their position at different levels. In contrast, WP4 measurements correspond to discrete points in the plot, as they are performed in static conditions once the sample is in equilibrium with the surrounding controlled environment.  
It was assumed that osmotic effects were negligible because distilled water was used. In this case, the difference in the thermohydraulic boundary conditions described between HYPROP and WP4 during their readings is very important, and therefore, the points from each equipment may not be fitted by the same equation due to scattering. Nevertheless, and as observed in Figure 3b, considering the average values from the two tensiometers, it appears that the points can be aligned in the same branch, and therefore, all were used in the definition of the first drying branch of the water retention curve. These experimental points were fitted using the van Genuchten equation [14]:  
\[S_{r}=\frac{G_{s}}{e}w=\left[1+\left(\frac{s}{p}\right)^{\frac{1}{1-\lambda}} \right]^{-\lambda}(S_{r,max}-S_{r,res})+S_{r,res} \tag{2}\]  
where \(S_{r}\) is the degree of saturation, \(w\) is the gravimetric water content, \(e\) is void ratio (assumed constant, further explained), \(G_{s}\) is the specific gravity of soil solids, \(s\) is total suction, \(P\) and \(\lambda\) are constants and \(S_{r,max}\) and \(S_{r,res}\) are, respectively, the maximum and residual degrees of saturation. The parameters found for the sample considered in the numerical analysis are in Table 1 for the drying and wetting branches. Data from the first drying and last wetting were used and the envelope curves were used for model calibration.  
No volume changes were measured during the tests performed in any sample, confirming the observations during the saturation of unconfined samples, which are not presented here [15]. Therefore, the soil was assumed to be stiff during the hydraulic paths applied and changes in the degree of saturation were attributed to be solely due to changes in water content. This motivated the use of thermohydraulic-coupled analysis in this work to simulate experimental data, instead of thermo-hydro-mechanical analysis.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter** & **Drying Branch** & **Wetting Branch** \\ \hline P (kPa) & 0.15 & 0.03 \\ \(\lambda\) & 0.26 & 0.25 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Calibration parameters of the WRC.  
Figure 3: Water retention curve found using both equipment: (**a**) first drying, showing the HYPROP measurements for both tensiometers; (**b**) complete set of experimental points, using the average measurements of the two tensiometers and including the curves adjusted for using Equation (2).