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Sydney Centre in Geomechanics and Mining Materials

Outstanding research in geomechanics and geotechnical engineering

We are at the forefront of research in geomechanics and granular physics, and aim to broaden our world-leading position in fields such as mining geomechanics and bulk material handling.

About the centre

The Sydney Centre in Gemechanics and Mining Materials (SciGEM) within the School of Civil Engineering was established in 2013 to capitalise on the outstanding pool of researchers with specialised skills and expertise in the field of geomechanics and geotechnical engineering.

SciGEM’s objective is to remain world leaders in the research fields of geomechanics, geotechnical engineering and granular mechanics. We are expanding into newer geo-environmental research issues such as soil contamination and bulk materials handling issues, including silo flow and conveying of particles, using our specialist laboratories such as DynamiX. We are focused on furthering our collaborations and relationships with industry and government in these sectors.

Our research projects

Our publications can be found in the hyperlinked academic profiles of each of the researchers. 

Our experts: Professor Itai Einav, Dr Yixiang Gan, Dr François Guillard, Dr Benjy Marks, Dr Pierre Rognon

Laboratories: DynamiX, Particles and Grains Laboratory

Our primary research goal is to identify the emerging properties of granular materials and establish the fundamental understanding of how grains flow, segregate, mix and crush, by merging complementary analytical, experimental and computational tools. Using our wide range of in-house computational models we carry out direct and precise simulations, with which we complement the experimental findings and cover the broader conditions tackled by industry and nature.

We use this body of observations to articulate simple and general mathematical formulae that accurately predict granular flows, accounting for the effect of grain size, shape and interaction modes. Our findings have advanced the resolution of important problems in geotechnical engineerings (prediction of landslide paths, novel and traditional foundations, etc.), geophysics (earthquake dynamics, heat balance beneath volcanoes), and mining and manufacturing (optimisation of material handling and mixing processes).

Our experts: Dr James Baker, Professor Itai Einav, Dr François Guillard, Dr Benjy Marks

Laboratory: DynamiX

The biggest problem with understanding granular problems is that we can't see inside them to observe what is happening. The DynamiX facility allows us to use large scale X-ray radiography and tomography to probe the internal structure of deforming granular materials, such as coffee, sand and snow. We have innovative methods for measuring the internal velocity fields, grain size distribution and particle shape orientation as they evolve over time. These methods have led to the investigation of a large number of problems, applicable to many industries, including bulk solids handling, coffee production and fibre-reinforced concrete.

Our experts: Professor David Airey, Dr Daniel Dias-da-Costa, Professor Abbas El-Zein, Dr Yixiang Gan, Associate Professor Gwenaelle Proust

Laboratories: Geo-environmental Laboratory, Geotechnical Research Laboratory, DynamiX

Clayey soils are a highly valuable material in a large number of applications in civil and environmental engineering, soil science, geology and agronomy – but one that can also create significant difficulties for engineers in many settings and may lead to landslides, sinkholes and structural foundation collapse. The unusual behaviour of clay soils owes a great deal to their geological genesis, complex chemical structure and physico-chemical properties, most notably the multiple ways in which water interact with clay particles at aggregate, particle and intra-particle levels.

Our research has two overarching goals. Firstly, to develop better theories and simulation tools at different spatial scales to account for and better predict the complex behaviour of clay (swelling and shrinkage, hydration and dehydration, fissuring and healing) under a range of practical environmental and engineering conditions. Secondly, we are investigating new forms of clay (for example, polymer-enriched bentonite) and new engineering designs with clay to maximise its engineering, scientific and social benefits. 

Our experts: Associate Professor Gwenaelle Proust, Dr Yixiang Gan, Associate Professor Luming ShenProfessor Abbas El-Zein, Dr Benjy Marks

Laboratory: Particles and Grains Laboratory

The shear strength of granular materials is ultimately determined at the interface scale between two grains. Key parameters include contact stiffness, friction coefficient and capillary interaction. While connecting the microscopic quantities with the engineering applications, fitting procedures at the grain scale were often made to achieve good agreements with macroscopic benchmark experiments.

Rather than using this end to justify the fitting processes, we are looking at extracting measurable material properties at the lower scale(s). In particular, we employ mechanical and chemical surface treatment for alternating the surface structure, microscopy (optical profilometer, atomic force microscopy) for characterising the surface topology, and nano-indentation for mechanical testing of the surface interaction. With the coexistence of multiple phases (solid, gas and liquid) in granular materials, we examine the dynamic interplay among them via computational (molecular dynamics, smoothed particle hydrodynamics, discrete element method, and lattice Boltzmann method) and experimental approaches developed in the lab.

We are also developing numerical tools for generating, analysing and simulating rough surfaces, and finally integrate these interfacial information into a hierarchical constitutive framework to pass essential parameters (and their evolution) to the engineering scale.

Our experts: Professor David Airey, Professor Itai Einav, Professor Abbas El-Zein, Dr Yixiang Gan, Dr François Guillard, Dr Guien Miao, Dr Pierre Rognon

Laboratories: Geotechnical Research Laboratory, DynamiX, Geo-Environmental Laboratory

The discipline of soil mechanics has historically focused on the behaviour of clayey sediments which underlie many of the world’s major cities and have presented many challenges to geotechnical engineering. Considerable research to understand the behaviour of sands which form extensive deposits, particularly around the coasts of many parts of the world, has revealed that the idealised soils tested in research laboratories do not represent real soils for which particle orientation and arrangement (structure) is important. There are many man-made (mined) soils that are intermediate between clays and sands.

Our research aims to better characterise these materials through careful testing in the laboratory using a range of soil testing apparatus. We conduct model experiments to evaluate the constitutive models developed from the material characterisation and use these models to investigate some challenging problems, such as understanding liquefaction in ship cargoes of mined ore materials; the onset of slope failures on submarine slopes; and the behaviour of soils subject to dynamic loading.

Our experts: Dr James Baker, Professor Itai Einav, Dr Benjy Marks, Associate Professor Gwenaelle Proust, Dr Pierre Rognon, Associate Professor Luming Shen

Although geomaterials are discrete, most practical engineering predictions require the articulation and solution of continuum mechanics model analogs. Our researchers have developed a range of such models grounded in rational thermodynamics and hydrodynamics principles. In formulating continuum mechanics equations for geomaterials it is important to acknowledge the interaction of particles with surrounding fluids. Irrespective of fluids the continuum state of dry granular materials depends on their density, stress, temperature and granular temperature that represents the motion of grains during flow. When wet, it is the interaction with fluids (air, water and their mixtures).

Add more complexity, brittle sand particles can crush, introducing new degrees of freedom that are not capture by such measures as the granular temperature. Our expertise in this area, has initiated classical formulation of breakage mechanics models, with the establishing of novel 5D continuum models, which include grainsize coordinated on top of the three space and one time coordinates. Apart from grain crushing, this new paradigm has successfully been applied to explain the segregation of particles by size and density.

Beyond immediate applications in geomechanics, our researchers continuously contribute to the broader field of mechanics, including to the capturing of multi-scale effects related to solid grains’ structure, twining and splitting in metal plasticity. 

Our experts: Dr Fernando Alonso-Marroquin, Professor Abbas El-Zein, Professor Itai Einav, Dr Yixiang Gan, Dr Benjy Marks, Dr Pierre Rognon, Associate Professor Luming Shen

Computational tools are substantially used throughout our research and involve a variety of in-house coded discrete element method models, cellular automata and stochastic lattice models, tracer method for advection-diffusion transfer problems; and in-house coded and commercially-available finite element method models, material point method models molecular dynamics packages; and surface evolvers, tessellation packages, and so on. This suite of modern computational tools enhances those traditional tools for slope stability, foundation and retaining wall design using limit analysis calculation tools, which have been important in our engagement with geotechnical companies.