Effects of grain morphology on suffusion susceptibility of cohesionless soils

Abstract

Transporting finer fractions inside the soil skeleton or the erosion of base soils within the filter are the two main challenges for earthen hydraulic structures, their foundations, and filter design. Soil particle morphology could influence pore size distribution and transport of fine grains; however, there is not sufficient knowledge on the effect of grain shape on internal erosion. Some experiments designed and conducted in the present study to evaluate the suffusion potential of aggregates with various shapes and different gradations. Particles with six types of grain morphologies and five gradations were collected, and 26 tests were performed. Furthermore, using 3D image processing and visual comparison, particle shape assessed in terms of three features, including sphericity, roundness, and roughness. Results indicated that particle shape influences flow rate, washed-out fine grains in permeameter wall, vertical strain, and mass loss. An increase in the sphericity and roundness causes an increase in the loss of fine grains, pipe in cell sidewall, and vertical strain. Concerning the particle regularity as an indicator of grain morphology, it was demonstrated that the grains with lower regularity are more resistant to suffusion, and thus the resistance to suffusion would decrease with particle regularity. Spherical glass bead and rounded/ medium sphericity specimens were more prone to suffusion at an equivalent or even lower hydraulic gradient than the soil samples with angular/low sphericity grains.