报告题目： Simulating Spalling with Bonded-Particle Model
报 告 人： David Potyondy 教授
报告时间：4月24日 09:00-12:00
报告地点：明辨楼A312
报告人简介：
Dr. Potyondy completed his PhD in Civil Engineering at Cornell University in 1993 and since that time has been employed by ITASCA, except for a two-year period from 2004-2005 as an Assistant Professor at the University of Toronto. Mathematical modeling of physical phenomena is the driving passion for his research and development work. He has developed and applied both continuum and discontinuum models to represent damage and flow processes on both a macro- and micro-scale. His primary research focus is micromechanical modeling using discrete-element methods in which a solid is represented as a bonded collection of discrete particles. He developed the bonded-particle modeling methodology along with Peter Cundall and continues to develop this methodology. The modeling methodology is embodied in the Particle Flow Code (PFC) and has been widely used. He has authored 67 technical papers, 57 reports, directed development of the PFC codes, given more than 46 PFC training courses that focus on microstructural modeling of rock fracture, developed the structural-element logic in the FLAC3D code, and developed novel techniques for applying micro-mechanical discontinuum models to fracture-related boundary-value problems that are not limited to rock-mechanics applications (interesting examples of which are shaving of human hair and grinding of wheat into flour).
报告内容摘要：
A history of the development of bonded-particle models with a focus on their suitability for studying the grain-scale micromechanics of spalling is presented. The modeling efforts began in 1998 with the creation of the initial 2D/3D parallel-bonded material consisting of a densely packed assembly of rigid and unbreakable disk/sphere-shaped particles. This was followed in 2010 by extending this model using the smooth-joint logic to create a 2D grainbased model in which agglomerates of rigid and unbreakable particles represent deformable, breakable, polygonal grains cemented along their adjoining sides. The 2D flat-jointed material was developed in 2012 (and extended to 3D in 2016) to overcome the tension-compression strength ratio limitation of the parallel-bonded material by introducing a notional finite-size interface at particle contacts. The interface may sustain partial damage and provides the rotational restraint arising from inter-granular interlock to mimic the microstructure of angular, interlocked rock grains. The 3D flat-jointed material was applied to study spalling in 2020 by constructing three flat-jointed materials that differ only in the shape of their rigid and unbreakable particles (spherical, Voronoi, and tetrahedral). It was found that the flat-jointed material with tetrahedral-shaped particles is better suited to model spalling than the flatjointed material with either spherical- or Voronoi-shaped particles. The development of bonded-particle materials has culminated in 2024 with the 3D SNBV material consisting of a Voronoi tessellation of rigid, breakable, polyhedral blocks with the PFC3D subspring network contact model at their interfaces. The SNBV material embodies all the microstructural features and damage mechanisms that occur at the grain scale of compact rock and exhibits behavior during direct-tension and compression tests that quantitatively matches the behavior of compact rock. Obtaining a fully 3D SNBV model that matches the laboratory-scale properties of intact rock and can be upscaled whereby particle sizes are increased and intact microproperties are degraded with a procedure that is not ad hoc to produce tunnel-scale damage localization in the form of spalling remains elusive and is the focus of ongoing research.
主办单位：地球科学与技术学院
科学技术发展研究院
