Engineers Australia

A thermodynamics-based formulation for coupled hydro-mechanical behaviour of unsaturated soils for failure analysis using the Smoothed Particle Hydrodynamics

Dr Gia Dat Phan

September 20, 2021

The nonlinear behaviour of unsaturated soils is governed by the fully coupled hydro-mechanical phenomenon due to the irrecoverable movement of particles and fluids. It is usually accounted for in constitutive modelling using separate evolution rules for plastic deformation and saturation, linked with two yield conditions for stress and suction. A new generic thermodynamics-based approach is developed to provide a more rigorous way to capture these underlying mechanisms. A special form of dissipation potential leading to strong inter-dependence of mechanical and hydraulic internal variables is used for the derivation of a single yield surface. A specific critical state model using a small number of identifiable parameters is derived from the proposed formulation. Its capabilities in predicting the drained and undrained experimental results are investigated to highlight the applicability of the present approach.

The developed thermodynamics-based approach is then implemented in the Smoothed Particle Hydrodynamics (SPH) for the solutions of Boundary Value Problems involving partially saturated porous media. The performance of the SPH approach is investigated through a range of numerical examples of the coupled flow deformation process under various loading and saturation conditions.

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