The knowledge of the internal stability of granular soils is a key factor in the design of granular or geotextile filters. To evaluate the internal stability of granular soils, different semi-empirical methods are generally used. Nevertheless, the results of these methods, on the same soil, can lead to different internal stability evaluations. In this paper, to evaluate the reliability of the semi-empirical methods available in literature, the internal stability of different granular soils, reconstituted by the authors and by other researchers, has been studied by means of theoretical and experimental approaches. In particular, the theoretical analysis of the internal stability was performed using the Simulfiltr method, developed recently by the authors, while the experimental evaluation of the internal stability was carried out by means of long-term filtration tests. The comparison of the internal stability analysis performed by means of semi-empirical, theoretical, and experimental methods showed that the semi-empirical methods are not always reliable. Therefore, on the base of these results, a new chart, in terms of minimum slope [S.sub.min] (%) of the grain-size distribution and of average value of finer percentage F, has been proposed to evaluate the internal stability of granular soils. Key words: grain-size distribution, internal stability, evaluation method, internal stability chart. La connaissance de la stabilite interne de sols granulaires est un facteur cle dans la conception de filtres granulaires ou de geotextile. Afin d'evaluer la stabilite interne de sols granulaires, differentes methodes semi-empiriques sont generalement utilisees. Neanmoins, les resultats de ces methodes sur un meme sol peuvent generer des evaluations de la stabilite interne differentes. Pour evaluer la fiabilite des methodes semi-empiriques disponibles dans la litterature, cet article presente une etude avec des approches theoriques et experimentales de la stabilite interne de differents sols granulaires, reconstitues par les auteurs et par d'autres chercheurs. Plus particulierement, l'analyse theorique de la stabilite interne a ete realisee a l'aide de la methode Simulfiltr, developpee recemment par les auteurs, tandis que revaluation experimentale de la stabilite interne a ete realisee avec des essais de filtration de longue duree. La comparaison entre l'analyse de stabilite interne realisee par les methodes semiempirique, theorique et experimentale a demontre que les methodes semi-empiriques ne sont pas toujours fiables. Ainsi, selon les resultats obtenus, une nouvelle charte de la pente minimal [S.sub.min] (%) de la distribution granulometrique et de la valeur moyenne du pourcentage plus fin F a ete proposee afin d'evaluer la stabilite interne de sols granulaires. [Traduit par la Redaction] Mots-cles: distribution granulometrique, stabilite interne, methode devaluation, charte de stabilite interne., Introduction The knowledge of the internal stability of granular soils is a key factor in the design of granular or geotextile filters (Moraci and Mandaglio 2008; Moraci et al. 2010). [...]