This training is an introduction to continuous modeling with FLAC2D and FLAC3D. At the end of the course, participants will master the graphical interface, documentation and the main modeling steps. Concepts are illustrated using a tunnel excavation example, from building the model geometry to results analysis. This introductory course provides the foundation for more advanced use of the software, which can be covered in more specific training modules.
The contact models provided with PFC are listed in the table below, together with their typical usage. The linear, rolling resistance linear, linear contact bond, and linear parallel bond contact models share many characteristics, and thus, are referred to as linear-based models. The linear contact bond, linear parallel bond, smooth joint, and flat joint contact models utilize the bonding concept wherein shear and/or tensile forces may develop as a consequence of relative motion. These models may be used to model Bonded-Particle Materials (BPMs).
Generic Adhesive Contact Model
Linear model, rolling-resistance mechanism and adhesion to give a cohesive granular material.
Built-in Contact Models
The linear, rolling resistance linear, linear contact bond, and linear parallel bond contact models share many characteristics, and thus, are called linear-based models. The linear-based models were also available in PFC 4.0. The distinct-element modeling framework within which they are embedded has been generalized and expanded in PFC 5.0 and PFC 6.0 so that their implementation differs from that in PFC 4.0; however, the contact mechanics embodied in these models remains the same so that their behavior in PFC 4.0 can be reproduced in PFC 5.0 and PFC 6.0.
The linear-based models provide two standard bonding behaviors embodied in the contact bonds and parallel bonds. These bonds can be installed at both ball-ball and ball-facet contacts. Both bonds can be envisioned as a kind of glue joining the contacting pieces. The contact-bond glue is of a vanishingly small size that acts only at the contact point, while the parallel-bond glue is of a finite size that acts over a {rectangular in 2D; circular in 3D} cross-section lying between the contacting pieces. The contact bond can transmit only a force, while the parallel bond can transmit both a force and a moment. By default, pieces are not bonded. Bonds are created by invoking the bond method. Bonds are removed when their strength is exceeded or by invoking the unbond method.
The bonded-particle modeling methodology defines materials and interfaces based on the contact models that are employed. The following materials and interfaces are defined. A contact-bonded material is a granular assembly with all contacts using the linear contact bond model. A parallel-bonded material is a granular assembly with all contacts using the linear parallel bond model. A flat-jointed material is a granular assembly with all contacts using the flat-joint model. A smooth-jointed interface can be inserted into the contact-bonded, parallel-bonded and flat-jointed materials by identifying the contacts near the interface and replacing their contact models with the smooth-joint model.
A BPM material is created by bonding selected contacts of a packed particle assembly. Contacts are bonded by invoking the bond method of the contact model. One can ensure the existence of contacts between all pieces with a contact gap less than a specified bonding gap (gb) by specifying gb as the proximity in the Contact Model Assignment Table (CMAT).