Inverse Methods for Characterising Hydraulic Properties of Soils Under Unsaturated Conditions


New indirect methods for estimating material properties of partially saturated soils are developed based on infiltration tests and inversion of multi-phase hydro-mechanical equations of soil behaviour.

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Professor Abbas El-Zein

Research Location

Civil Engineering

Program Type



A large number of geoenvironmental problems require scientist and engineers to understand and predict the behaviour of soils under partially saturated conditions in the vadose zone. The two more important hydraulic properties under unsaturated conditions are the water retention curve, q(h), which relates the water content q to water pore pressure h and the hydraulic conductivity function kunsat(h). Both of these functions are highly non-linear relationships that are difficult, time-consuming and expensive to determine experimentally. These difficulties have contributed to the slow dissemination of unsaturated soil mechanics into geoenvironmental practice where the soil is most commonly, and often erroneously, assumed to be saturated. This can lead to potentially unsafe or over-conservative designs. Cost-effective techniques for determining hydraulic properties by using infiltration or evaporation tests, combined with an inverse solution of the Richards equation, have shown promise in the past. However, these techniques have been mostly developed in the soil science literature for sandy and silty soils. Their application to clay soils remains very limited. The goal of the project is to develop new tests, also based on inverse solutions, that can accurately provide a measurement of hydraulic functions q and kunsat for various soils. The project will hence consist of a combination of experimental and numerical investigations and can lead to an important breakthrough in the field of unsaturated soil mechanics. 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 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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water retention, hydraulic conductivity, Hydro-Mechanical, finite-element method, inverse solutions

Opportunity ID

The opportunity ID for this research opportunity is: 2420

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