AGS NSW Research Award for Research in Geotechnical Engineering or Engineering Geology

FINALISTS

This year three (3) research award finalists have been chosen to provide their presentations to the wider geotechnical community and they are:

Mason Crumpton

Adaptive Discontinuity Layout Optimisation for Upper Bound Geotechnical Stability Analysis

Amin Y. Pasha

Modelling the Volume Change Dependency of the Soil-Water Characteristic Curve

Alessandro Tengattini

Cemented Granular Materials: A Micro-mechanics Based Study

Mason Crumpton

Adaptive Discontinuity Layout Optimisation for Upper Bound Geotechnical Stability Analysis

ABSTRACT

Pioneered by Smith & Gilbert in 2007 Discontinuity Layout Optimisation is a novel procedure for computing rigorous upper bounds on parameters governing the collapse of a geostructure. The procedure shares much of the simplicity of traditional analytical methods and generality of contemporary finite element methods. Efficiency considerations have forced early DLO analyses to employ meshes generated on a grid of nodes spaced at regular intervals, which may include a small number of off grid points. Reasonable solutions can be obtained quickly for many problem types using coarse regular meshes. However, when producing design charts, modelling soils with high friction angles, or investigating unfamiliar problems, more refined meshes are preferred so that greater accuracy may be attained.

A new procedure developed by Crumpton et al. (2014) for efficiently generating meshes on an irregular grid of nodes has been combined with an interpolation error estimate to produce an adaptive node refinement algorithm. Applying the adaptive algorithm to a number of geotechnical stability problems has shown that it is able to provide highly accurate solutions using only modest computational resources.

BIOGRAPHY

Mason Crumpton obtained a bachelor’s degree in civil engineering with first class honours from The University of Newcastle in 2010. After completing his undergraduate degree he received an Australian Postgraduate Award scholarship to study under the supervision of Laureate Professor Scott Sloan, Professor Andrei Lyamin, and Associate Professor Andrew Abbo.

Mason’s research is centred on extending and applying methods for computational limit analysis, with a particular focus on adaptive techniques for Discontinuity layout Optimization. Having presented the initial findings of his research internationally Mason is now finalising his dissertation.

Amin Y. Pasha

Modelling the Volume Change Dependency of the Soil-Water Characteristic Curve

ABSTRACT

Soil-water characteristic curve (SWCC) builds a fundamental relationship between the amount of water available in a soil and its matric suction and has extensive practical applications in various science and engineering disciplines such as geotechnical engineering, agricultural science, and soil physics among others. Past experimental evidence has shown that SWCC evolves with soil’s void volume. Models currently available in the literature for capturing the volume change dependency of the SWCC are mainly phenomenological in nature requiring an extensive experimental programme for parameter identification which renders them unsuitable for practical applications. This work presents two modelling approaches to account for the volume change dependency of the SWCC in a deformable soil. The first approach is based on energy considerations accounting for hydraulic hysteresis and volume change dependency of the scanning curve and the second model is based on a fractal approach considering the changes in pore shape with loading. Features of the proposed models are discussed and their application is demonstrated through comparison between numerical predictions and experimental data for different types of soils obtained from the literature. Very good agreement between model predictions and experimental results is observed highlighting the ability of the proposed models in capturing the volume change dependency of the SWCC.

BIOGRAPHY

Amin Y. Pasha is conducting his research in Geotechnical Engineering at the Centre for Infrastructure Engineering & Safety (CIES), School of Civil & Environmental Engineering, UNSW. He has completed his BEng in Civil Engineering, and MEng in Geotechnical Engineering, and has worked for several years in the consulting engineering companies prior to the commencement of his PhD. Amin has previously conducted research on liquefaction analysis of sheet pile quay walls, and physical and numerical modelling of pollution transport through soils and their remediation techniques. His current research is focused on hydro-mechanical coupling in unsaturated soils. In 2014, he received the Dean’s Award for Excellence in Postgraduate Research at the Faculty of Engineering, UNSW. Also in 2015, he was awarded The Civil & Environmental Engineering / Geotechnical Engineering Prize, for the best performance in Research Presentation at UNSW. His research has led to several publications in peer-review journals as well as presentations in international conferences.

Alessandro Tengattini

Cemented Granular Materials: A Micro-mechanics Based Study

ABSTRACT

Most engineering solutions to advanced geotechnical problems re- quire adequate predictions of geomaterial behaviours in terms of stiff- ness, strength and failure properties. My thesis develops constitutive models for cemented granular materials (e.g. sandstones) which successfully predict all these aspects, based on few, physically meaningful parameters.

A key feature of my models is the connection established between the macroscopic stiffness, strength and failure properties, and grain- scale features such as grain size and the local strength of both grains and cement.

Thanks to recent technological advances in x-ray microtomography, it is now possible to inspect these phenomena directly. My thesis develops tools to extract, for the first time, quantitative information about the grain-scale mechanisms occurring in cemented granular materials. This allows both to enhance the models and to validate their prediction of the microstructure, which is at the core of open problems such as permeability evolution and sand production.

BIOGRAPHY

Alessandro obtained his BE in Environmental Engineering (geohazard, Hons1) at Polytechnic University of Milan where I discovered my passion for Geotechnics. To deepen my understanding of it, I started a ME in Civil Engineering (Geotechnics, Hons1) at Polytechnic University of Milan. I then moved to Grenoble, France, a leading university in geomechanics, where I obtained my MRes (geomechanics, Hons1). During my permanence there I met Itai Einav, in sabbatical leave. Thanks to him I discovered the worlds of micro- mechanics and constitutive modelling (among many other things). Fascinated, I decided to follow him to Sydney for my PhD. During my first year I developed and validated a new model for cemented granular materials. The success of the model pushed me to further investigate the micro-mechanical phenomena at its core. I therefore moved back to Grenoble for one year, to take advantage of their advanced experimental facilities and processing tools. With a better understanding of each phenomenon, I returned to Sydney where I worked at the improvement of some aspects of the model, while advancing the tools to extract ever more exhaustive data from my experimental campaign.

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