The role of breakage-dependent critical state lines in constitutive modelling of sand under axisymmetric drained and undrained loads: A comparative study

Abstract

Particle breakage usually takes place within sand when subjected to external loading, which changes the critical state line (CSL) and stress-strain behavior of sand. To consider such effect, different expressions for the CSL with consideration of particle breakage have been proposed, which can be sorted in two categories: (i) CSL through explicit incorporation of particle breakage ratio into the e – ln p′ relation, (ii) CSL through implicitly empirical correlation, e.g., e – p′ 0.7 and e – exp(p′ζ ) relations. However, limited studies were made on comparing the performances of these expressions. This study inspects the efficiency of three representative CSLs from categories i and ii, for SANISAND modelling of sand. It was found that all the CSLs can capture the constitutive responses of sands under axisymmetric drained and undrained loads, to some extent. However, e – p′ 0.7 and e – exp(p′ζ ) relations are comparatively simple and share an equivalently accurate performance at low to medium high pressures, whereas e – exp(p′ζ ) relation works the best among others at high pressures. To more highlight the physical role of particle breakage, the CSL in category i can be suggested. Otherwise, the CSLs in category ii are recommended in modelling practices, because of the comparatively succinct expressions and less model parameters.