Posted Tue, 09 Oct 2018 00:14:20 GMT by Matthew Simons Student

I am currently developing a model to assess inflow to an underground mine. The model domain will be roughly 14x8 km with the mine located in the middle (total extent of mine tunnel system being 3x1 km). I have a .dxf file representing the underground workings, but am unsure of how to work with it in FEFLOW and mesh around it as I have not used this type of file before. Some of the questions I have include:

-How do I horizontally discretize the mesh around the underground workings? Importing the file to FEFLOW has it displayed as an AutoCAD DXF File in the Maps panel and not an element in the supermesh, meaning that I cannot discretize more finely around the workings.

-How do I properly manipulate the layers passing through the geometry of the mine so that, when I assign my seepage nodes, they are properly located?

Thanks in advance.

Posted Tue, 09 Oct 2018 09:01:12 GMT by Björn Kaiser
Thank you for your mail. Before I give a reply, please provide the following information:

1. Do you intend to represent the underground mine by 1D Discrete Features or fully discretized?
2. Which file-types (e.g. dxf, shp) with what kind of geometry (lines, polygons, points) do you use to generate the 2D Supermesh?
3. Do you get an error or a warning notification in the Log-Panel after you tried to import the file? If yes, what does the message say?
4. Which FEFLOW version are you using?
Posted Tue, 09 Oct 2018 20:16:17 GMT by Matthew Simons Student
1. This is something I have yet to decide on, but I think that it would be better for me to fully discretize the workings and use seepage nodes so that I can simulate the progressive drilling of the tunnel.

2. I am using a .dxf file that represents the underground workings. I realized that I had to convert this to supermesh lines, though now when I try and generate a mesh (using the Triangle mesh generator) it throws the error "Invalid mesh topology near point x=20715, y=18640.2!". The supermesh lines cross over each other (as the workings exist at the same x y coordinates at different depths), could this be responsible for the error I am getting?

3. I don't receive an error when importing the file.

4. I am using FEFLOW

Thank you, Bjorn.
Posted Thu, 11 Oct 2018 06:20:25 GMT by Peter Schätzl
If you have lines crossing each other, you may also have line vertices very close to each other in the different depths of the tunnels. As the vertices are used as mesh nodes, very small distances may lead to problems in mesh generation. So you'll have to avoid vertices with extremely small distances in the add-ins (either by pre-processing, or by manually adjusting the lines and/or vertices in FEFLOW.

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