Valutazione della stabilità interna dei terreni granulari

The evaluation of the internal stability of a granular soil in contact with a filter is a very important aspect for the design of a filtering system. The erosion of the base soil takes place when the size of the constrictions of the filtering transition are too large and therefore are not able to retain the particles of the base soil entrained in the flow. This phenomenon produces significant volume changes within the soil and the resulting deformation may not be admissible with the limit state of the structure. In some cases, the phenomenon can lead to failure of the granular structure in contact with the filter with the consequent associated damage. In the paper, the main methods available in the literature to evaluate the internal stability of granular soils are described and critically discussed. Therefore, the recent research developments on internal stability achieved by the authors are illustrated. In particular, two methods, considering the grain size distribution of granular base soil, both validated by long term filtration tests, are described in detail.