Dyke designs like the above two examples are well-suited to the PLAXIS 3D LE extrusion feature. This feature avoids many common pitfalls that are possible when attempting to use 3D drawing tools to solve this type of problem.

The basic process is as follows:

1. Create a 2D model in the appropriate software (PLAXIS 2D LE)
2. Ensure model follows the design rules required for 3D models (see below)
3. Use the “Save As” option to save the 2D model as a 3D extruded model

Create the 2D Model

Here is a slightly simplified 2D model based on the first image above, built using PLAXIS 2D LE:

This reflects the real-world scenario correctly but cannot be extruded to 3D as-is. For a successful extrusion, every point in the model must be capable of inclusion in a surface, and 3D models in PLAXIS LE products require surfaces to be contiguous in 3D (often referred to as a 2.5D surface). Put another way, surfaces cannot fold over themselves; every point on a surface must map to a unique elevation. To fix this, one or more “extra” layers can be added, to ensure that every point in the model can follow a left-to-right continuous path without requiring a vertical wall.

By adding a new layer with the same material, we get a functionally identical model, but we also satisfy the 3D extrusion requirements.

As seen here, an extrusion path is now possible (shown highlighted above) and thus the model will extrude to 3D successfully.

Note that because the middle layer was added with lines going both up and down, an extra surface was created that isn’t needed. There is also an extra region on the left that can be removed as a result of this. After deleting the extra surface and combining the two adjacent regions into one, the result looks like this:

The second example from the top of this document is even more straightforward. Here’s a slightly simplified 2D model for that case:

All paths already satisfy the 3D extrusion rules, so the result looks like this:

As with the first example, some post-extrusion simplification is possible. In this case, all the regions can be combined into one (and the layer material assignments updated for consistency). The result is as follows:

Using “Save As” to Create the Extruded 3D Model

The “Save As” option allows some changes to be applied to a model, in addition to a simple name change. In this case, we wait to do the following:

1. Change the “System” option to 3D, which enables extrusion
2. Set a new name
3. Enter a minimum and maximum Y value range in the “Spatial” tab, which is enabled once the 3D option is selected

The graphical image will display how the X and Y coordinates are treated in the 3D output model.

Conclusion

Advanced 3D tools such as PLAXIS Designer offer a lot of power to the user, but such power is not always necessary when creating 3D models. The 3D extrusion tools that exist in PLAXIS LE offer a simpler and faster alterative.