The validity of this new model is confirmed by data from triaxial drained and undrained compression and extension tests for clays with different overconsolidation ratios, true triaxial tests with different Lode's angles, and cyclic loading tests. Compared with the Cam-clay model, the UH model requires only one additional clay parameter, the slope of the Hvorslev envelope. Based on the SMP criterion and the corresponding transformed stress method, the proposed model can be applied conveniently to three-dimensional stress states. The key feature of the model is the adoption of a unified hardening parameter that is independent of stress paths. The UH model can model many characteristics of overconsolidated clays well, including stress–strain relationships, shear dilatancy, strain-hardening and softening, and stress path dependence behaviour. Draw a trendline in Excel using power function. Draw the Eoed/pref and pressure/pref on logarithmic axes. A current yield surface is used to describe over-consolidated behaviour, and a reference yield surface to describe the yield characteristics corresponding to normally consolidated clays. Using the same approach described before, we can calculate the Eoed as below: Take the 1/mv values and pressures from the oedometer tests. Based on the relationship between the current yield surface and the reference yield surface, a new model, called the three-dimensional unified hardening model for over-consolidated clays (the UH model), is proposed in this paper.
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January 2023
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