AGS Tasmania Chapter 2022 Symposium
Keynote speakers: Professor Nasser Khalili, Professor Andrew Chan, Ms Delia Sidea, Dr Mohammad Vahab, Dr Hamed Lamei Ramandi and Dr Hongyuan Liu
While the symposium is free, we ask all attendees to register below, for catering purposes.
A viscoplastic model is presented for creep and strain rate behaviour of soils with particular reference to capturing drained, undrained, primary, and tertiary creep. The model is formulated in the context of the bounding surface plasticity using the consistency viscoplastic framework and the critical state theory. The formulation proposed enables capturing the accumulation of viscoplastic strains upon loading and unloading, as well as creep rupture observed in overconsolidated clay. The time-dependency of the soil response is accounted for by defining the size of the bounding surface as a function of viscoplastic volumetric strain and strain rate. The model meets the consistency condition and allows for a smooth transition from rate-dependent viscoplasticity to rate-independent plasticity. Simulation results and comparisons with experimental test data are presented for several drained and undrained creep tests, constant strain rate tests, and stress relaxation tests, to demonstrate the application of the constitutive model.
PSM Professor and Scientia Professor Khalili has about 30 years of experience in geotechnical engineering, both as a consultant and as an academic/researcher. Prior to joining The University of New South Wales in 1993, he was responsible for managing the geotechnical group in the Chicago Office of the consulting firm Dames & Moore. He is currently the President of the Australian Association for Computational Mechanics (AACM), Fellow of Institution of Engineers Australia, Fellow of Australian Geomechanics Society, and Fellow of Academy of Technological Sciences and Engineering (ATSE). His research interests lie primarily in the areas of mechanics of unsaturated soils, soil plasticity, and mechanics of multi phase multi porous media. He is the recipient of many prestigious international awards including: Chandra Desai Medal from International Association for Computer Methods and Advances in Geomechanics (IACMAG) in 2014, and Valliappan Medal from International Association for Computational Mechanics (IACM) in 2016.
The physical behavior of brittle material such as rock before and after fracture is examined. They are governed, in part, by two mechanisms viz. surface-to-surface interaction; and the fracture breakage of the individual surfaces. Surface interaction is predominantly described by the contact condition of the surfaces, whereas particle breakage depends on the stress state within each grain. Both the grain interaction and its corresponding stress state have to be appropriately accounted for when modelling the behavior of granular media. To achieve these objectives, this seminar examines the use of Combined Discrete Element – Scaled Boundary Finite Element Method (DEM-SBFEM) based on the framework of Polygon-SBFEM. The use of arbitrary sided polygonal particles in SBFEM enable the morphology of each grain to be modelled using a single polygon thus making this method more efficient than the use of FEM in the stress analysis in individual particle. The flexibility of this approach adapts very well to the evolving geometries of the granular medium during the loading process. The effectiveness of the developed method is demonstrated through parametric studies to highlight the role of the particle breakage on the behaviour of granular media at both the macroscopic and particle scales.
Prof. Chan joined the University of Tasmania, Australia, in March 2015 and he is currently Professor of Engineering. He has a wide research interest. He is one of the world leading experts in the use of the finite element method of static and dynamic fully coupled soil and pore-fluid interaction and the author of two comprehensive Finite Element packages for deformable porous media and pore fluid interaction. His recent interest, besides the use of Scaled Boundary Finite Element Method and Discrete Element Method for the modelling of particle breakage, includes simulating the breakage of glass under hard body impact using the combined finite-discrete element method and modelling dynamic saturated soil and pore fluid interaction such as fluidization using combined Discrete Element Method and Lattice Boltzmann method. He is subject editor for the Journal of Applied Mathematical Modelling and on the editorial board of Computers and Structures.
Physics-Informed Neural Networks (PINNs) are a class of Deep Learning (DL) that incorporate a series of physical laws, frequently described in the form of partial differential equations (PDEs), to steer the learning towards the solution for sparse training datasets, which could not be plausible with classic DL algorithms. The prosperity of PINNs is attributed to substantial algorithmic advances (e.g., graph-based automated differentiation) and major software developments (e.g., TensorFlow , Keras). DL is best suited to recognize the mapping relations between inputs/outputs given a training dataset. A beneficial remedy can be offered by physics-informed deep learning, which provides the network model along with the laws of physics governing the system. This can rectify the issues associated with the missing ingredients induced by the sparsity of data, uncertainties, or other less understood factors. We explore the application of the Physics-Informed Neural Networks (PINNs) in a range of conventional geotechnical and structural engineering problems. An Airy-inspired PINNs solution is proposed for the analysis of foundation problems. As another improvement, Fourier series are elaborated to investigate the solution of plates deflection. We find that enriching the feature space using Airy stress functions/Fourier series can significantly improve the accuracy of PINN solutions for biharmonic PDEs. We construct custom physics-informed functions next which pertain to fundamental solutions of fracture mechanics. We show the proposed framework can easily captures the singular solution and characteristic parameters accurately on both noise-free and noisy data regimes. Finally, the application PINNs to forward and inverse analyses of pile-soil interaction problems is presented.
Mohammad is a lecturer in the School of Civil and Environmental Engineering at UNSW. He completed his PhD in Computational Geomechanics at Sharif University of Technology in 2015. He immediately joined UNSW as a research associate, where he is currently employed. He specializes in the thermo-hydro-mechanical coupling processes in saturated/unsaturated porous formations. His research interest is the development of robust numerical simulation frameworks for the analysis of fractured porous media using the state-of-the-art computational methods, such as Extended Finite Element Method (XFEM), Non-differentiable Energy Minimisation using Discontinuous Galerkin Method (DG), and Phase-field Method (PF). More recently, Mohammad investigates the application of deep learning in the study of complex mechanical response of geo-infrastructures by means of the Physics-Informed Neural Networks (PINNs). He is a Chief Investigator (CI) and Data Manager in the Research Hub on “Resilient and Intelligent Infrastructure Systems (RIIS)”, which aims to sustainability, serviceability, resilience, planning, decision making, and safe operations in geotechnical, structural, and mining engineering applications. He is also a CI in ARC Discovery Project (DP) entitled, Non-differentiable Energy Minimisation for Modelling Fractured Porous Media. Mohammad has been the recipient of the excellent paper award by International Association for Computer Methods and Advances in Geomechanics (IACMAG 2022) Junior Individuals, the best paper awards in the 3rd Australasian Conference on Computational Mechanics (ACCM 2019), best paper award in the 1st International Conference on Geomechanics and Geoenvironmental Engineering (iCGMGE 2017) Early Careers, and Bronze Medal in 13th scientific Olympiad of civil engineering (Iran, 2008).
Cable bolts and rock bolts are widely used as anchoring systems in the mining industry. In the past two decades, reports on the frequency of stress corrosion (SCC) failure of bolts in underground mines have been increasing. Premature failure of bolts due to SCC is an unresolved worldwide problem in underground structures, particularly underground mines. Such a failure threatens underground mine workers’ safety and the operations’ economic viability. Since 2002, UNSW Sydney has continuously worked on this problem. UNSW’s long-term corrosion research program has resulted in several significant outcomes, such as identifying SCC as the main cause of bolts failure, determining hydrogen-induced SCC driven by microorganisms as the mechanism of failure, and developing laboratory and in-situ testing methodologies for bolts. These have been achieved by continuous support from the industry and government and a unique multidisciplinary research team that includes mining, groundwater, geology, materials, chemistry, and microbiology experts. The team is currently developing prevention methodologies to provide a solution to the industry.
Hamed is a Senior Lecturer in the School of Minerals and Energy Resources Engineering at UNSW Sydney. He is a multidisciplinary researcher with academic and industry experience in both science and engineering. His research spans a wide range of geological and geotechnical problems. His key research interests include digital rock analysis, fractured media, multiphase flow through porous media, rock characterisation, reactive fellow, and geomechanics with applications to mineral exploration and extraction, space resource utilisation, hydrogen storage, CO2 geosequestration, ground control, water and environmental studies. Most of Hamed’s current research projects are industry-oriented, with close collaboration with the mining industry,
Combined finite-discrete element method (FDEM) incorporates the advantages of the continuous and discontinuous methods and thus can seamlessly model the transition from continuum to discontinuum during material damage and fracture. Correspondingly, FDEM has been applied and further developed by a number of researchers around the world for various engineering applications involving in the damage and fracture of a range of materials. A both two-dimensional (2D) and three-dimensional (3D) hybrid finite-discrete element method (HFDEM) has been developed at University of Tasmania (UTAS) for the failure and collapse analysis of geostructures, which has also been parallelized on the basis of general-purpose graphic-processing-units (GPGPU) using compute unified device architecture C/C++. This presentation will first review the unique features of HFDEM2D/3D compared with other FDEM implementations around the world, which mainly include efficient contact detection algorithms, novel contact activation schemes, and extrinsic cohesive zone models besides GPGPU parallelisation. These implementations have made HFDEM about 8,000 to 61,000 times faster, which pave the way for modelling the stability and collapse of geostructures and resultant debris fragmentation and flow involved in a large number of irregular-shaped and non-cohesive debris. HFDEM is then applied to investigate the collapse process of irregular-shaped and non-cohesive particle heaps and the excavation-induced slope instability, as well as the resultant complex debris fragmentation and flow process.
Hong is a senior lecturer at UTAS, a fellow of Engineers Australia, a chartered professional engineer and a member of Australian Geomechanics Society (AGS). He was the Chair of the 12th Australia and New Zealand Young Geotechnical Professional Conference (YGPC) in 2018, Co-chair of the 4th Australasian Conference on Computational Mechanics (ACCM) in 2019, and National Representative (2017-2019) and Committee Member (2011-2019) of AGS Tasmanian Chapter. Before being appointed as the founding geotechnical lecturer at UTAS in 2010, he had worked in University of Queensland as a research fellow and University of Sydney as a postdoctoral fellow. He completed his PhD at Lulea University of Technology in Sweden, and Master and Bachelor degrees at Northeastern University in China. His research interest focuses on tunnelling, rock fracturing, and computational geomechanics. He is the founding or primary authors of three comprehensive geotechnical software including both 2D and 3D hybrid finite-discrete element method (HFDEM), 3D elasto-plastic finite element method (TunGeo) and 2D damage-mechanics and random probability – based finite element method (RFPA). In recent years, he has been leading an international team to develop HFDEM for geotechnical applications, which has claimed several national and international awards including the Best Paper Awards in the 3rd and 4th ACCM in 2018 and 2019, respectively; Excellent Paper Award in the 5th International Society of Rock Mechanics (ISRM) Young Scholar’s Symposium in 2019; Best PhD Thesis Award by AGS Tasmanian Chapter in 2020; and Excellent Paper Award in the ISRM 11th Asia Rock Mechanics Symposium in 2021. On this research interest, he has also graduated 3 PhD students as the primary supervisor in recent 3 years.
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