## 2 Materials and Methods
### Experimental Setup
#### 2.2.1 Hydrop  
For the tests, a HYPROPTM device (HYdraulic PROPerty analyzer [10]) developed by UMS was used. It was developed to determine the water retention curve and the unsaturated conductivity of soils during desiccation. A saturated sample of soil is placed inside a container closed at the bottom and with the top opened to the atmosphere. The container has two tensiometers located at two different levels in the sample (shafts with 50 and 25 mm, and the tips are placed 32.5 and 12.5 mm from the inner base of the container; see Figure 2) and a temperature sensor.  
Soil suction (water tension) is measured considering the water inside the shaft via a porous ceramic tip (Al\({}_{2}\)O\({}_{3}\) porous sintered material, with air entry value of 800 kPa) and measured by a pressure transducer placed in the base. The measurement range of the tensiometers is from \(-85\) kPa (water tension) to 2 kPa (water pressure), with 0.15 kPa accuracy in the range from 0 to \(-80\) kPa. The temperature sensor can measure temperature between \(-30\) and \(70\)\({}^{\circ}\)C, with a tolerance of \(\pm 0.2\) K in the range of \(-10\) to \(30\)\({}^{\circ}\)C.  
Figure 1: Grading size distribution of several samples of the soil.  
The container is placed on a scale (measurement range from 0 to 2.5 kg and an accuracy of 0.1 g) and the total mass is recorded during the evaporation process, as well as suction measured with the two tensiometers and the temperature. The mass changes are then used to calculate the volumetric water content to be associated to the corresponding suction value, leading to the definition of the water retention curve. The measurements finish when one of the tensiometers runs dry or the mass difference becomes negligible.  
Suction measurements using the HYPROPTM device were carried out in undisturbed samples extracted from core tubes (70 cm diameter). The specimens for the HYPROP equipment (a steel ring 80 mm diameter and 50 mm height) were trimmed using a cutting ring and removing the excess soil with a wire saw. The gap between the ring and the intact core (respectively, 80 and 70 mm in diameter) was filled with the same soil, trying to compact the material at the same natural density. Two holes were created in order to install the tensiometer shafts. These holes, each with the depth of the respective shaft and done using a specific tool, were filled with a slurry of the same soil while the shafts were not inserted. Six samples were tested.  
The shafts were screwed into the sensor unit after being refilled with water and degassed in advance. Then, the sample was placed on the center of the HYPROPTM base unit in order to fit both shafts in the undisturbed part of the specimen. The ring containing the soil was carefully placed on a perforated plastic base covered by filter paper, then transferred into a tray filled with water and left in it overnight to saturate the sample. The dimensions and weight of each sample were taken before and after this procedure.  
At the end of the test, each sample was measured and weighed before being oven-dried at 50 \({}^{\circ}\)C until reaching constant weight. Such temperature for drying was adopted due to the presence of organic matter in the soil (assuming that the amount of water removed was just within the pore space between the soil grains). This final weight allowed us to estimate the dry mass of the sample. All values of water content computed were related to the value after this drying (assumed to be null). The experimental procedure was designed specifically for this test, intending to simulate the exposition of climate actions.