Morphological Perspectives to Quantify and Mitigate Liquefaction in Sands

Abstract

Though the qualitative effects of grain size and grain shape on the tendency or resistance of a sand to liquefaction are well established, quantitative correlations between them are elusive. Most of the studies in this direction used conventional methods to quantify the size and shape of the grains, which include sieve analysis and visual observations. The current study evaluates the size and shape of sand grains through image-based characterizations and relates them to the liquefaction potential of the sand measured in laboratory cyclic simple shear tests. Microscopic images of sand particles were captured and analyzed using MATLAB codes to arrive at the mean particle size, sphericity, roundness, and surface roughness of the sand particles. Cyclic simple shear tests were carried out on sands and sand-like glass beads of different sizes and sands with rounded and angular grains. Results showed that smaller grain size and regular shape of the particle with high sphericity and roundness increase the liquefaction tendency by many folds. In the undrained cyclic simple shear tests carried out in the study, spherical particles liquefied in 8 cycles, whereas river sand with subrounded particles liquefied in 13 cycles and manufactured sand with relatively elongated particles liquefied in 16 cycles, particle size being almost same for these three assemblies. Decrease in the liquefaction potential of loose granular assemblies with an increase in grain size and shape irregularity is correlated to the microscopic mechanisms and discussed in light of their tendency for densification, fluid flow patterns and porewater pressure development. Tests with geosynthetic inclusions showed definite reduction in liquefaction potential.