<p>This study investigates the influence of grain size distribution (GSD), initial water content (<i>w</i>_i), and aggregates shape on the segregation behavior of granular materials subjected to vertical vibration. A series of controlled laboratory experiments was conducted using twelve different GSDs at initial moisture contents ranging from 0 to 10%. The results show that both the extent and continuity of the GSD significantly affect the occurrence of water upwelling and segregation of solids. Sub-rounded aggregates exhibit higher levels of segregation than sub-angular aggregates. Water content plays a dual role: increasing moisture reduces segregation up to an optimal saturation threshold, beyond which segregation increases again. No water migration was observed when the maximum particle size (<i>D</i>_max) was less than 2.5&#xa0;mm, and the fines content (<i>D</i> &lt; 0.08&#xa0;mm) remained below 10%. However, materials with discontinuous gradations and fines contents exceeding 10% exhibited upward migration of fines and localized liquefaction when the degree of saturation exceeded 50%. The findings also highlight the critical role of the intermediate particle fraction (0.08&#xa0;mm &lt; <i>D</i> &lt; 5&#xa0;mm) in controlling saturation variations, beyond the influence of the coarsest and fines fractions. Although restrictive grain size specifications can help limit segregation, the study emphasizes the need for appropriate construction practices and compaction methods to maintain homogeneity in granular layers.</p> Graphical Abstract <p></p>