Discontinuous Discrete Methods for Solving the Multi-phase Hydro-mechanical Behaviour of Partially-saturated Soils


The goal of the project is to develop robust finite-element type solvers of the equations describing the multi-phase hydro-mechanical behaviour of partially saturated soils, hence addressing commonly encountered convergence problems caused by strong nonlinearities present in key constitutive equations, such as the water retention curve.

Please contact the supervisor directly at the following email address for any enquiry regarding this opportunity: abbas.elzein@sydney.edu.au


Professor Abbas El-Zein

Research Location

Civil Engineering

Program Type



Soil above the water table, known as the vadoze zone, is either partially-saturated, or nearly-saturated by capillary rise, with water held between soil particles under negative (tensile) pressure. Either way, the behaviour of the soil acquires added complexity, compared to saturated media, due to the presence of an air phase in the soil and the dependence of key thermal, hydrological and mechanical material properties on the water content of the soil. In addition, key constitutive hydrological and mechanical equations exhibit sharp nonlinearities (e.g., sharp drops in water content of soil for small changes in negative pore pressures). Hence, numerical solutions of coupled equations of hydro-mechanical behaviour often suffer from lack of robustness and convergence problems. The goal of the project is to develop more robust and accurate numerical scheme for solving equations of water flow (Richards equation), water and vapour flow, as well as the coupled multiphase hydromechanical equations based on Biot’s theory. The project will develop and test discontinuous element methods, adaptive spatial and temporal meshing techniques as well as semi-analytical finite elements. The developed codes will be validated against analytical and numerical solutions and will be applied to a range of flow and stability engineering problems that occur in the vadose zone. The successful applicant will be trained in the theoretical and experimental investigation of coupled thermo-hydro-chemo-mechanical (THCM) analyses of unsaturated soil mechanics. He or she will develop an expertise in the design and performance assessment containment systems for the protection of subsurface ecosystems. Papers are expected to be published in one of more leading journals in the field such as international J for Numerical Methods in Engineering, International J for Numerical and Analytical Methods in Geomechanics and Water Resources Research. The work will be presented at leading international conferences in the field. The School of Civil Engineering at the University of Sydney has a long tradition of cutting-edge research and is ranked 20th in the world by the QS World University Rankings by subject. The successful candidate will join a thriving community of scholars at the School with a large and diverse group of PhD and Master’s students.

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unsaturated soil, vadose zone, multi-phase, finite-element method

Opportunity ID

The opportunity ID for this research opportunity is: 2421

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