In dealing with a partial model the need can arise, to make changes to the layer structure of the model. The reasons for this can be of different nature:

Recent studies and drilling results require a change in the depth position of layer boundaries.

The processing of detailed questions in the partial model requires a more differentiated analysis of individual geological units, so that a further subdivision of certain model layers is required.

For the correct representation, for example, of imperfect wells or built components (sheet piles, tunnels, etc.) is another vertical division of individual model layers necessary.

 

Since the added vertical layers of the partial model have no equivalent in the overall model such an assignment has to be created. The following cases are differentiated:

 

In the partial model has been no change in vertical layers. In this case the boundary nodes correspond to the intersection of the two meshes, and the layer mapping is automatically correct. Image (a) of the following figure illustrates this situation.

In the partial model, the depth position of layer boundaries, for example, was changed due to new drilling data. However, a vertical mesh refinement was not carried out, so that the number of layers and the assignment between partial and overall model is identical. In this case, the assignment automatically leads to a correct result. If the depth position of layer boundaries was also changed to the edge of the partial model, the assignment nevertheless leads to a correct result. Since there is a unique layer assignment, the depth of the layer boundaries is defined by the imported model part. This means if the overall model is opened first and then the partial model is imported the depth of the boundary nodes of the partial model overrides the depth of the overall model. This situation is shown in image (b).

One or more layers in the partial model were vertically refined, except for representing a more differentiated geological structure or a proper hydraulic consideration of measures (eg imperfect wells, vertical wells, sheet piles, tunnels, etc.). Such a situation is schematically illustrated in image (c). In this case, a layer assignment must be performed at the import of the partial model. In the general case the vertical refinement is carried out to the edge of the partial model, so that the depth of the existing model layers has changed there. In this case, an automatic assignment of the model layers is not clearly possible.

 

Assignment of layers between partial and overall model

 

In the third case, the number of layers in the partial model has changed. The added layers of the partial model must exist formally in the overall model after the import, ie outside the partial model they merge geometrically together with hitherto existing layers. The assignment of the boundary nodes is controlled during the import of the partial model.

Although these eliminated layers are actually not considered in the simulations, they must be maintained for the modelling and for the node and element numbering.

Thus, if another partial model is imported into an overall model in which a vertically refined layer already exists because of a previous import, should as many of the existing coincident layers be used.

 

Conclusion: In general, the refinement of the layers of the partial model should not be performed on the model boundary. Thus, the depth position of the added layers can be properly assigned to the layer boundaries of the overall model.

 

Installation of the partial model in the overall model