## 3 Experimental Results
### Cyclic Tests in the HYPROP Equipment  
Figure 4 presents data measured in the test performed in the HYPROP equipment: inner and outer temperatures, relative humidity and changes in water mass and suction measured in the long and short shafts. In total, seven drying-wetting cycles were applied, followed by final drying.  
Figure 4: Data logged during drying and wetting cycles: (**a**) inner and outer temperature; (**b**) RH% and mass loss ratio; (**c**) net sample weight; (**d**) suction.  
As shown in Figure 4, the variation of water mass decreased during drying due to evaporation and increased during wetting because it was added manually. It is worth noting that the temperature inside the sample increased relatively fast at the beginning of the test to reach the temperature of the room, probably because the water added was at room temperature and reached the bottom of the cell. After this initial increment, the inner temperature was kept approximately constant in the remaining test period.  
Concerning suction, as expected, higher values were detected in the long shaft upon wetting because it is the tensiometer closest to the upper border in contact with the atmosphere. The suction recorded during the drying-wetting cycles applied allowed for quantifying hydraulic hysteresis, information necessary to be used later in the model simulation. Figure 5 presents the curves recorded during the drying-wetting cycles, respectively, in the long and short shafts. The curves at the final of each cycle do not coincide and it appears that a residual suction remains at the end of the test. This is because full saturation was not achieved in any wetting cycle due to the fact that the soil was not initially saturated and water was added only to compensate for water loss during drying.  
Hysteresis was observed in both tensiometers' curves, but for the long shaft, the drying branch was above the following wetting branch, as usual, while in the short shaft, the wetting branch was above drying. This can be explained by transient readings and the delayed response of the short shaft because it is far from the sample surface, the upper boundary where water is being exchanged with the room atmosphere.  
As when the water retention curve was fitted using Equation (2), the average values of the tensiometer readings were used to find the envelope curves of the cycles, and therefore fix the expressions of the two branches of the WRC to be used in the simulation, as well as hysteresis. The drying branch was defined considering the curve of the first drying, while the wetting branch was defined considering the curve of the last wetting. The slope of the transition between both was also determined to be used in the numerical model.  
Figure 5: HYPROP measurements during the four drying–wetting cycles for the tensiometers (first cycle in black; last cycle in grey): (**a**) short shaft; (**b**) long shaft; (**c**) average values.  
Concerning boundary conditions, although no mechanical load was applied, the vertical displacements were restrained at the base and horizontal displacements were restrained at the vertical side, corresponding to the lateral wall of the cell. Both the base and lateral walls were considered impervious but allowed for temperature exchanges.