## 4 Discussion  
The present study reported and discussed laboratory data of the thermo-hydro-mechanical state of a natural unsaturated clayey soil from the Paola DOC outcropping at Pisciolo (with reference to the soil sample between 0.3 and 1 m depth, which is part of the topsoil), obtained by different monitoring techniques and probes. Section and temperature measurements were collected to characterize the behavior of the TEROS 21 water potential sensor, comparing its readings with those obtained from more established methods, i.e., the FP technique and HCTs. During the process of reaching hydraulic equilibrium in both test 1 and test 2, the porous stones of the sensor modified the water content in the sample, as water exchange was established between the stones and the specimen. Water flow from the ceramic discs to the soil sample was activated to achieve hydraulic equilibrium when an initially wet sensor was used to measure the suction of a soil sample with a higher suction than that of the ceramic discs. In this instance, the soil specimen may have undergone a wetting process due to the water lost from the saturated ceramic discs, which were drying. Conversely, water flow from the soil sample to the ceramic discs was activated to achieve hydraulic balance when a dry sensor was used to measure the suction of a soil sample with a lower suction than that of the ceramic discs. Under this scenario, the soil dried while the unsaturated ceramic discs of the sensor were wetted. As already mentioned by [PERSON] et al. [7], the hysteretic behavior of the ceramic discs (i.e., differing drying and wetting curves) is not defined, which is reflected in the suction values measured in the soil samples. This has a clear impact on the monitored suction values, depending especially on the initial state of the TEROS 21 probe [7]. This behavior may also be partly related to the size of the specimen, which might have been too small compared to the size of the probe. However, using a larger sample volume could introduce soil heterogeneity and potentially reduce the representativeness of the measurements across different samples [30; 39]. The formation of a clear hysteresis loop (Figures 3 and 7) indicates that the sensors exhibited path-dependent behavior, with distinct responses during wetting and drying cycles. This hysteresis effect is crucial for understanding the performance of the sensors, as it highlights the need to consider the \"history\" of water content changes when interpreting sensor data, particularly for in-situ measurements [33]. The analysis of the data in Figure 3 indicates a non-negligible influence of the initial moisture conditions of the TEROS 21 porous stone (wet or dry) on the measured suction and temperature values. When using the dry TEROS 21, higher suction values were recorded in the soil sample compared to measurements obtained with a wet sensor. Additionally, the initial moisture state of the sensor appears to affect the equilibrium time, as shown in Figure 4. However, it seems that it is not only the initial condition of the sensor that matters but also the water content of the soil specimen to be monitored. Indeed, the closer the moisture conditions of the TEROS 21 and the specimen, the faster the attainment of the hydraulic equilibrium. It is also worth mentioning that the transient hydraulic process that is activated when the sensor is in contact with the soil specimen is also influenced by the interface's hydraulic condition. The air trapped in the interface can slow down the seepage process required to reach the hydraulic equilibrium, potentially even halting it under certain conditions [7]. Consequently, the logged value obtained by the dry sensor may be affected by a similar troubling issue. In contrast, when adopting wet sensors, this effect is likely less significant, facilitating a more reliable attainment of hydraulic equilibrium.