## 4 Discussion
### Methodological Limitations and Implications of the Results  
The methodology employed in this study presents inherent limitations owing to the simplified approach used to characterize the behavior of unsaturated soils. A key assumption in this research is that the matric suction remains constant or varies only slightly during loading, based on undrained conditions resulting from the rapid application of stress. However, the lack of active suction control during loading can allow the internal redistribution of water and air, leading to hydromechanical processes, such as phase changes between air and water. However, these phenomena were not observed in this study. Specifically, the matric suction was indirectly estimated using the SWCC  
Figure 21: Graph of undisturbed sample behavior between depth and: (**a**) Saturation; (**b**) Matric suction; (**c**) Maximum compressive strength; (**d**) Elastic Modulus. curve obtained using the filter paper method. This technique is inherently discrete and indirect and does not enable real-time monitoring of suction evolution during deformation. Consequently, the degree of coupling between the hydraulic and mechanical processes during loading cannot be fully assessed, which introduces uncertainty in the interpretation of soil behavior in terms of effective stress. Owing to these constraints, suction-sensitive parameters such as the \(\phi^{\text{b}}\) angle cannot be reliably determined from the adopted methodology. Instead, they can only be approximated under total-stress conditions. Therefore, the results obtained should be interpreted as representative of the initial suction state of the samples rather than a full characterization of their behavior throughout the loading process up to failure. The measured shear strength and stiffness correspond to a simplified condition in which an undrained response is assumed, and the effects of suction are implicitly incorporated into the total stress. This approach aligns with the framework proposed by [PERSON] and [PERSON] [3] for cases where active suction control is not feasible. The empirical equations and correlations developed in this study should, thus, be considered valid only within the specific geotechnical and hydrogeological contexts analyzed. This includes the characteristics of the tested silty soil and the ranges of evaluated water content and suction. The application of these findings to other soil types or materials with different geological histories, particularly those with distinct macrostructural features, requires additional studies using advanced laboratory techniques that allow active control of suction. Such investigations should involve static tests such as direct shear and triaxial testing, as well as cyclic tests such as cyclic triaxial tests, resonant columns, and bender element testing. These tests should be performed under controlled suction conditions to better capture the coupled hydromechanical behavior of unsaturated soils. This is particularly important for undisturbed samples, whose natural heterogeneity makes their responses more complex and difficult to predict. In addition, the undisturbed samples examined in this study showed limited variation in natural water content, which prevented obtaining data within the high suction range necessary to fully assess the influence of wetting and drying cycles on the geomechanical parameters of the soil. Instead, a seasonal approach was adopted to analyze precipitation fluctuations throughout the year to infer the stage of the wetting-drying cycle at the time of sampling. To acquire data representative of high suction conditions in undisturbed samples using this methodology, it would be necessary to collect additional samples during the driest months or to extract multiple samples from each stratum and subject them to controlled drying under controlled humidity and temperature conditions, thereby preserving their natural drying behavior.