## 3 Results
### Test 3: Comparison of Measurements with Undisturbed Soil Test Result  
The water content values of the specimens at the end of the first and second tests were compared with the equilibrium suction values obtained from both the wet and dry sensors, as well as the FP. Additionally, retention data from undisturbed samples, determined using the FP method and the HCT, are presented. All collected data are shown in Figure 7, depicting the matric suction as a function of the water content.  
At a water content range larger than 25%, in the second test, the suction values obtained from the FP method were only slightly higher than those measured by wet and dry sensors. Conversely, at a lower water content (i.e., <25%), the FP test results were lower than those from the sensors. In agreement with [PERSON] et al. [7], when considering the corrected value for the water content of the material in contact with the sensor (as shown in Figure 5), the retention states measured by the wet sensor shifted upward in the water content-suction plot, while for the dry sensor, these shifted downward. This adjustment reduces the discrepancy between the FP and the TEROS 21 probe measurements. Furthermore, the TEROS 21 sensor demonstrated repeatability, as the measurements from test 1 and test 2 were in close agreement, indicating the reliability and consistency of the data.  
Comparing the results obtained by means of TEROS 21 for both test 1 and test 2, with the FP and HCT measurements on undisturbed samples, some differences can be observed. All the techniques were found to give reasonably good and consistent measurements for the undisturbed samples for suction values higher than 100 kPa (Figure 7). However, with high water content values, the measurements obtained with the HCT tended to be lower than those obtained from the TEROS 21, i.e., the HCT provided smaller values for suction. This is potentially due to, again, the retention properties of the ceramic discs of the TEROS 21. Specifically, at high water contents, a substantial change in the water content of the discs resulted in only a minor variation in the suction value. Indeed, the WRC of the porous stones became nearly vertical for suction values between 1 and 30 kPa.  
When the drying paths were applied to the unsaturated specimens (test 3), it was observed that the water content decreased only slightly, despite a significant increase in the matric suction. This circumstance corresponds to an AEV [5] at a relatively high suction level. When the suction values exceeded 800 kPa, the slope of the retention curve fitting  
Figure 7: Comparison of the water retention data determined by means of filter paper technique and the ICL high-capacity tensiometers together with the water content-suction result obtained from the experiments.  
the data increased significantly, aligning well with previously reported values for the same material [26; 39]. Following the AEV and the associated 'volumetric collapse' [30], the retention curve exhibited high stiffness and minimal shrinkage, eventually transitioning into a constant specific volume stage, during which the degree of saturation continued to decrease [39]. Although the WRC tended toward a residual degree of saturation at very high suction values, the FP measurements were terminated upon reaching a suction of approximately 25 MPa, which can be considered its upper limit [38; 45].