Internal Stability Assessment of Granular Soils Based on Graphical Method to Determine the Delimiting Particle Size

Accurate assessment of the internal stability against suffusion for granular soils is very essential in order to prevent geotechnical structures failure. Many methods are available for this purpose with variety degrees of accuracy and usage complicity. This study is presenting a simple and a reliable method to assess the internal stability. The delimiting particle size of the granular soil is computed based on graphical method, and then the controlling constriction size, D
c35
, of the primary soil skeleton is obtained based on an empirical equation and compared with the diameter of fine particles, d
85
. The soil is considered as internally stable if it has D
c35
⁄d
85
<0.75. The assessment of new method was compared with the most frequently used ones, as well as experimental tests, and its assessment was found to be fairly good.