Investigation of spatial scale effects on suffusion susceptibility

Internal erosion processes in earth structures and their foundations may increase the failure risk of such structures. Suffusion, one of the main internal erosion processes, selectively erodes the fine particles that move through the voids formed by the coarser particles. In literature, several suffusion susceptibility investigations were already published with various tested specimen sizes. However, the influence of the specimen size on suffusion susceptibility is not well established. The objective of this study is to investigate this influence by comparing results of suffusion tests performed on six different soils, with two different sized devices. First, this study highlights the complexity of the suffusion process, which is a combination of three processes: detachment, transport, and possible filtration of the finer fraction. The results also show a decrease of the critical hydraulic gradient with the size of the specimen. The proposed interpretative method is based on the energy expended by the seepage flow and the cumulative loss dry mass. This method permits one to obtain the same suffusion susceptibility classification for both specimen sizes.