Applying Gradation Methods to Assess the Internal Stability of ASTM C33 Sand

Abstract

Internal erosion in granular filters used to control the seepage flow in embankment dams threatens the safety of these structures. In granular filters using non-cohesive granular soils, relatively fine particles can be transported by seepage through the voids between relatively coarse particles by the suffusion mechanism. The granular soils in which the suffusion mechanism develops are defined as internally unstable soils. For the suffusion mechanism to develop, the void size, distribution, and shape, which PSD curves can determine, are first evaluated. If there is a suitable environment for material transport, the design is realized by considering the hydraulic gradient of the seepage flow. This study performed the internal stability analysis of ASTM C33 sand, which meets the filter design criteria for many base materials with different gradation methods. Accordingly, it was determined that USBR-modified ASTM C33 sand is a stable soil that cannot be subjected to suffusion according to the internal stability analysis methods considered.