Particulate mechanics framework for modelling multi-physics processes in fracturing geomaterials
The potential of particulate mechanics was explored with the purpose of developing a single software modelling framework in which to model multi-physics geomechanical problems. Individual particulate models were developed for solid, fluid and granular material phases, building onto the existing Distinct Element Modelling (DEM) environment Particle Flow Code in Three Dimensions (PFC3D), with the intention that they could be combined to represent a geomechanical problem of any configuration. Advantages of utilising PFC3D were firstly, its inbuilt feature allowing inter-particle bonding so that, in the limiting case, solid material could be represented and secondly, its embedded coding language, FISH, which allows the creation of user defined variables and functions which may be used to manipulate and modify the basic DEM code. The Particle Solid Model (PSM) employed a bonded particle assembly with the concept of constructing a determinate lattice to replace a continuum material. Basic particle interactions were handled by the DEM behaviour inherent to PFC3D and complex behaviour, such as fracturing, was realised through additional code written in FISH. The Particle Fluid Model (PFM) was created with the concept of developing a macroscopic particle representation of a fluid where the particles moved freely with the flow. Fluid behaviour was implemented by preventing physical contact of the DEM particles through force-separation laws representative of pressure and viscosity fields. These were again realised via FISH code. The Particle Proppant Model (PPM) would be implemented simply through the inherent capabilities of the PFC3D DEM code and would be used to represent granular material on a grain for grain basis. After initial development of the individual models, benchmark tests were carried out to evaluate their basic capabilities.