We need to model the dynamic response of a dam under seismic loading. The dam geometry is complex, not easily simplified in a manner that lends itself to structured meshing, as seen below:
what would be a recommended way of creating such a mesh for analysis in FLAC3D?
I would also recommend creating an unstructured mesh for this geometry by using Griddle 2.0. It looks like the bottom surface is very uneven and I may guess that there is another domain that connects to it. All these initial geometries/meshes can be imported into Rhino and meshed with Griddle.
One thing to be aware of is that dynamic timestep is quite sensitive to the quality/shape of zones. Thus, when meshing with Griddle it is still advisable to smooth highly uneven surfaces/meshes as much as possible to get best elements/zone quality. This can be done by re-meshing all input meshes with high Ridge angle (GSurf command) or even by using Rhino’s build-in Quad remesher (QuadRemesh command; be careful with this one, it may create pretty meshes but they will be overly smooth and far from the original shapes). Also, if using GSurf, it would be better to remesh into quadrilateral-dominant or pure quad mesh then use volume mesher GVol in HexDom mode to get a variety of zones (mostly bricks/hexes) for the dynamic analysis.
For more details on Griddle 2.0, check documentation, webinar or check a training course.
Note that FLAC3D 7.0 and 9.0 provide built-in unstructured volume meshing via zone generate from-geometry command. However, its use may be limited as users have to provide cleaned-up conformal surface meshes for the command to operate on and it does not consider nested volumes.
Hopefully this helps.