Grain Geometry Import and Group in UDEC

Hi all, I have imported dxf files as geometry in UDEC for different types of grains. Is there any way to cut the block by these grain dxf files and group them?
Many thank.

Hi Jia. Technically you can cut a block using any imported DXF geometry using the UDEC command:

block cut geometry ‘geometry_set_name’

The tricky part for this scenario is that the geometry must cut through an entire block in order to be recognized as a new block. You can’t cookie cutter a new block in the middle of another block. You can get around this by extending construction cuts from the block you want to generate across the block you want to cut into. This is commonly done with tunnels and joints in both 2D and 3D. See example below. Note that the slope cut differentiates the “air” above the slope (purple) and the rock below. But that the rock is made up of two blocks (red and cyan) since a construction joint was needed to embed three tunnels into it. The properties for the this joint are set to that of the rock to prevent any slip, separation, or closure occurring along it.

Although you could try to create a FISH function to rotate and translate the smaller blocks, this could be tricky. You could try to pre-create your model cuts in a CAD program like Rhino3D ensuring that all the smaller blocks are connected to the outer domain boundary and then import this as a DXF and cut the initial large domain block.

If you want to group certain cuts/joist together, you could do this incrementally (block by block or groups of connected blocks) using the jointset-id keyword. This is generally easily than trying to group post-cutting.

PFC2D has the ability to use templates to construct clusters of particles and rigid blocks of pre-defined shapes and fill a region, but UDEC does not. If you are modeling granular or rocky materials, PFC may be a better choice; it also has more contact models to choose from. You can get a feeling for PFC templates in this PFC3D example.