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Cohesive Crack Model in Coupled Hydro-Mechanical Theory of Partially Saturated Soils


The fissuring and healing of clay is modeled using a novel approach, within a finite-element framework, that will allow the design of new materials and new geotechnical structures with the capacity for autonomous repair.

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Professor Abbas El-Zein.

Research location

Civil Engineering

Program type



Fissuring of clay causes a number of problems in geoenvironmental and geotechnical engineering, especially in foundation systems, waste containment, pollution control, slope stability, roads and embankments. Early attempts at modelling fissuring have been based on highly idealised frameworks (such as linear elastic fracture mechanics or cohesion spring systems) which can account only qualitatively for some general aspects of observed behaviour. Most existing models make an assumption of full saturation which is often unrealistic for fractured soils. The multi-phase, hydro-mechanical theory of unsaturated soils – first established in the 1990s – has been applied in the early 2000s to the desiccation problem but these studies usually either predict the onset, rather than the evolution of cracks, use constitutive mechanical equations that are unsuitable for clay or do not allow for fracture closure under changing load or moisture conditions. Recent advances have seen the application of particle-based methods which are powerful but computationally expensive. Incorporating the cohesive crack model – a more realistic characterisation of the mechanical interactions between the faces of a fissure – into a hydro-mechanical theory of unsaturated behaviour offers a highly promising development because of its ability to better track the evolution, including closure, of the fissures. The goal of the project is develop a cohesive crack theory of fissuring and healing in clay by combining a new hysteretic cohesive crack model with a fully-coupled, hydro-mechanical theory of behaviour of unsaturated soils and a new ‘healing’ finite element type. The project will be part of an Australian Research Council Discovery project starting in 2017 and will give the candidate an opportunity to be part of a nationally and internationally significant research effort. The successful applicant will be trained in the theoretical and experimental unsaturated soil mechanics and geoenvironmental engineering. He or she will develop an expertise in macro- and pore-scale modelling as well as laboratory techniques in geomechanics. Papers are expected to be published in one or more leading journals in the field such as Geotechnique, Applied Clay Science, Water Resources Research and/or International for Numerical and Analytical Methods in Geomechanics. The work will also 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, is ranked 20th in the world by the QS World University Rankings by subject and has been ranked 12th in the world by QS in 2013. The successful candidate will join a thriving community of scholars at the School with a large and diverse group of PhD and Masters students.

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Opportunity ID

The opportunity ID for this research opportunity is 2171

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