Calculating the State Parameter in Crushable Sands: Fid-Bau Portal

Calculating the State Parameter in Crushable Sands

Ciantia, Matteo O. / O’Sullivan, Catherine

The state parameter (ψ) measures the distance from the current state to the critical state line (CSL) in the compression plane. The existence of a correlation between both the peak angle of shearing resistance $(ϕ_{p}^{'})$ and peak dilatancy and ψ is central to many constitutive models used to predict granular soil behavior. These correlations do not explicitly consider particle crushing. Crushing-induced evolution of the particle size distribution influences the CSL position, and recent research supports the use of a critical state plane (CSP) to account for changes in grading. This contribution evaluates whether the CSP can be used to calculate ψ and thus enable the prediction of the peak angle of $ϕ_{p}^{'}$ and peak dilatancy where crushing takes place. The data considered were generated from a validated DEM model of Fontainebleau sand that considers particle crushing. It is shown that where ψ is calculated by considering the CSL of the original uncrushed material, there can be a significant error in predicting the material response. However, where the CSP is used, there is a significant improvement in our ability to predict behavior irrespective of whether the CSP is accurately determined using a large number of tests or approximated using crushing yield envelopes. It is shown that the state parameter calculated using the previously available definition can give a false sense of security when assessing the liquefaction potential of potentially crushable soils. This contribution also highlights the stress-path dependency of the relationship between $ϕ_{p}^{'}$ and ψ whichever approach is used to determine ψ.