Critical State Behaviour of Weakly Bonded Soil in Drained State
Abstract
A series of consolidated drained triaxial test was performed on weakly bonded soils that were artificially prepared by mixing sand (87%) and kaolin (13%). To create weakly bond strength, samples were fired at 500°C for 5~h. A critical state (CS) concept was used to interpret the results in order to describe the behaviour of the studied soil. Defining the CS is not always straightforward. Several tests showed changing in deviator stress q and volumetric strain \epsilonv up to the end of tests. Hence, defining the CS requires careful assessments on q\textendash\epsilona, Δu\textendash\epsilona, q\textendashp' and v\textendashln p' spaces which were performed. A `discontinuity' approach was applied to position the CS on dilatant path in v\textendashln p' spaces after considering stress-strain and volumetric strain curves. The critical state line in a v\textendashln p' space from bonded samples exhibited differences to the destructured samples. This suggests that the influence of cementation bond is substantially clear at lower stresses but as stresses increase beyond the stress yield, cementation degradation becomes more significant. The effect of bonding can be clearly visualised from the normalisation of the stress paths of destructured and bonded samples. \textcopyright 2018, \textcopyright 2018 Informa UK Limited, trading as Taylor & Francis Group.