When modeling a geotechnical problem using PLAXIS it is important to follow a generalized methodology. The methodology will avoid potential issues using numerical methods, specifically PLAXIS FEM (Finite Element Method). Additionally, having a methodology will help maximize time efficiency during model creation.

First, it must be emphasized that the FEM (Finite Element Method) gives an approximation of the solution using numerical methods. Therefore, it is technically difficult to model all the physical aspects of a normal building site. Specifically, these physical aspects cover both a 2D framework (plane strain or axisymmetric) or even a fully dedicated 3D model (although to a lesser extent). Often when building a model, simplifications are usually necessary.

The two main drivers that produce results in PLAXIS 2D and 3D are the applied loading and the soil/rock models. Superficial aspects, such as drawing or importing any superstructure building shape, drawing or importing a highly-detailed stratigraphy that has a negligible impact on global geotechnical model behavior, and other superficial graphical features (on a scale of 1% [1/100] of the model dimensions) do not help produce an efficient modeling strategy. In contrast, they hinder an efficient workflow by potentially sinking time unproductively.

Therefore, we have a recommended workflow when dealing with complicated site geometries to maximize time efficiency.

A step-by-step procedure can be followed when creating any complex model. Please note, these are suggestions and may not be applicable in every modeling scenario. Generally, this workflow will be appropriate for most modeling situations. Therefore, during the process of building up the model you should:

1. start with the soil layers in Soils mode (if applicable, depending on the model);
2. make any intelligent simplifications in the structures, keeping in mind it is important for the program to have the correct loading, rather than a detailed drawing;
3. introduce a small part of the geometry in Structures mode, rather than creating the whole model all at once;
4. further consider what simplifications can be made to the geometry that retains the applied loading conditions to the soil;
5. switch to Mesh mode to see that the model intersects without problems;
6. generate and inspect the quality of the mesh;
7. go back to Structures and add the next part of the geometry.

Perform steps 3-7 until you have the desired model built.

With this procedure, you can make sure that you always have a model that can be properly intersected and give a valid mesh (maintain lowest quality around 0.01 when possible).

However, problems may be encountered during this procedure. By following these steps it will be easier to find out the cause of the problem.

Note that in some cases, the layering might be complex, too. In that case, the structural part of the geometry can be introduced first, and then try to create the soil layers of the model (simplified when needed).