JCERSM|第81期学术讲座: 混合有限-离散元法在地质材料断裂及地质灾害防治中的发展应用|主讲人: Hongyuan Liu

The rapid development of modern society has resulted in the construction of increased geostructures, many of which are constructed in sensitive areas prone to natural disasters posing impressing geohazards. When these geohazards are not appropriately mitigated and prevented, the damage, fracture, failure and collapse of the geostructures occur from time to time. Thus, to mitigate and prevent the geohazards, it is imperative to study the fracture and fragmentation of geomaterials under various loading conditions. Numerical methods have nowadays become powerful and robust tools of investigating the geomaterial damage and fracture. Among them, 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 fracture and fragmentation of geomaterials, which has also been parallelized on the basis of general - purpose graphic – processing - units (GPGPU) using compute unified device architecture (CUDA) C/C++ and is free to download and use. This presentation will first review the history and state-of-the-art of FDEM and introduce some unique features of HFDEM compared with other FDEM implementations around the world. The unique features of HFDEM to be introduced in this presentation include computationally efficient semi-adaptive contact activation approaches (ACAA), both statistics- and grains- based multi-scale heterogeneities, rate-dependent elasto-plasticity model for both cohesive and solid elements, novel extrinsic cohesive zone model based on master-slave algorithm, fast convergent geostatic analysis with local damping and mass scaling, as well as efficient  fragment search algorithm for generating fragment size distribution. Some other advanced features of HFDEM will also be briefed, which mainly include mesh-independent and easily GPGPU parallelized contact detection, efficient tetrahedron to points and accurate volume-based contact interactions, memory efficient contact damping, discrete fracture network, shear strength reduction, and multiphysic coupling. HFDEM is then calibrated by modelling the fracture and fragmentations of geomaterials under static and dynamic loads such as the split Hopkinson pressure bar (SHPB) – based dynamic Brazilian tensile tests, uniaxial, biaxial and triaxial compression tests as well as cylindrical blast tests. After that, HFDEM is applied to investigate the collapse process of irregular-shaped and non-cohesive soil heaps, the control of the excavation damage zone during deep tunnelling using contour blasting, the excavation-induced rock burst in jointed rock mass with high in-situ stress, the excavation/blasting-induced slope stability as well as the result complex debris fragmentation and flow process, and even Antarctic iceberg calving due to climate changes. It is finally concluded that HFDEM is a valuable, novel and efficient numerical tool to investigate the fracture and fragmentation of geomaterials under various static and dynamic loading conditions as well as the instability and collapses of geostructures and resultant debris flow involving a large number of irregular-shaped cohesive and non-cohesive debris for mitigating and even preventing the geoharzards.

Dr Liu is a senior lecturer at UTAS, a fellow of the Institution of Engineers Australia, a chartered professional engineer, a member of Australian Geomechanics Society (AGS) / International Society for Rock Mechanics & Engineering and editorial board members of International Journal of Rock Mechanics and Mining Science, Underground Space and other 3 international journals. 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 Acting/Deputy Chair (2018-2019), National Representative (2017-2019) and Committee Member (2011-2019) of AGS Tasmanian Chapter. Before being appointed as a geomechanics lecturer at UTAS, he was a research fellow at University of Queensland and a postdoctoral fellow at University of Sydney. He completed his PhD and Licentiate degrees at Lulea University of Technology in Sweden, and his master’s and bachelor’s degrees at Northeastern University in China. His research interest focuses on computational geomechanics, geomaterial fracture and tunnelling, which has resulted in 104 peer-reviewed journal publications, several national and international awards such as excellent paper awards by ARMS2021, ISRM2019 and ACCM2018, three comprehensive geotechnical software including HFDEM to be introduced in this presentation, a citation number of 3666-4750 and an h-index of 36-41 (Scopus-Google).