Experimental study on fractal characteristics of seepage-induced failure in granular soil

Seepage-induced failures in granular soils pose a potential hazard for geotechnical engineering, but the types and mechanisms of seepage failures have not been fully clarified. In this paper, the mass fractal dimensions of testing soils were used to describe the cumulative mass distribution of particles, which was closely related to the uniformity coefficient, fine content, porosity, dry density and permeability coefficient. A series of hydraulic tests were performed to show seepage failure behaviors of sandy gravels, coarse sands and fine sands. By linking the mass fractal dimension to the critical hydraulic gradient, a zone segmentation approach for seepage failure types was proposed to distinguish seepage failures, including piping, suffosion and heave. Piping failure originates from internal instabilities in inhomogeneous soils and has been observed in sandy gravel samples. Suffosion occurs in coarse sand samples due to external and internal erosion of loose particles. Heave failure is dominated by fine content and has been observed in fine sand samples. By comparing the changes in the mass fractal dimension before and after seepage failure, it is feasible to predict piping failure in sandy gravels and suffosion in loose coarse sands, while it is almost impossible to predict heave failure in fine sands.