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.
UDEC uses a factor of safety calculation for stability analyses based upon the “strength reduction method”. A “factor of safety” index can be defined for any relevant problem parameter by taking the ratio of the calculated parameter value under given conditions to the critical value of the parameter, at which the onset of an unacceptable outcome manifests itself. Typically, application of the strength reduction method produces one single factor of safety per simulation, corresponding to one global minimum stability state. However, the ability to calculate multiple minimum states may be of interest, for example, to generate a safety map for a complex slope profile such as a benched cut or a slope with a berm (see following figure). The explicit dynamic solution method employed in UDEC allows multiple local stability surfaces to be identified in one simulation.
With factor of safety contouring, material strengths are reduced in increments by a strength reduction factor. Unstable states for the model are identified at the global minimum state and then beyond that state. Unstable states of the model are identified at each stage as an assembly of gridpoints with velocities above a specified average value. The current strength reduction factor is assigned to unstable gridpoints for later contouring. If the strength is reduced in small intervals, progressively more regions of gridpoints can be identified as unstable. By monitoring the velocities, it is possible to delineate the regions of unstable gridpoints by different strength factors and produce a plot of factor of safety contours.
When a View pane (plot) is active, the toolbar includes a group of buttons to set the current mouse mode to one of four states: Select, Query, Center, and Distance. When the Query mode is selected, as highlighted in the image below, you can use the mouse cursor to inspect your model. Clicking on a location in the model will provide a list of one or more objects that can be queried (e.g., block, zone, gridpoint). Selecting an object from the menu will open a dialog that contains model information pertinent to it as shown; data can be copied to the clipboard or logged.
As shown in the magnification bubble in the screen capture above, even when query mode is not active, the mouse cursor constantly relays general model information based on its position and nearby objects.
The track command is used to track blocks, zones, and grid points. Show positions over time using the particle tracking plot item.