Basis for creating a tunnel is an l-structure, which level corresponds to the central axis of the planned tunnel. The height can be assigned as the attribute KKKK.
The following functions are available:
The menu item Generate geometry-contours (
) is active when an l-structure is present. If this item is activated, the desired l-structure can be selected with the left mouse button, and after pressing the right mouse button, the following input window appears:
The inner radius and the wall thickness are given in m. The refinement of the cross section defines how the tunnel is shown. In this case, the tunnel cross section is shown as a heptagon. The refinement of the axis corresponds to the menu item Contour 
Edit l-structure divide in n parts.
Instruction for the generation of tunnels
Create an l-structure of the central axis of the tunnel, values (attribute KKKK) at the start and end points of the structure correspond to the NN level of the central axis and are interpreted from the program as height, regardless of the data type.
Call the menu item Special features Tunnel Generate geometry-contours …
Select the l-structure with the left mouse button and calling the parameter menu with the right mouse button, input the parameters: The contours parallel to the central axis appear.
Delete existing mesh in the area of the tunnel, create new nodes and elements.
Important: Reassign attributes, especially the ground level and Z-coordinates in the new mesh area.
Call the menu item Special features Tunnel Generate geometry-contours again, select the tunnel axis and re-enter parameters.
Via the menu item Special features Tunnel Generate tunnel the new tunnel is created.
The result can be visualized in the menu View vertical section.
The previously created tunnel-contour looks in the top view as follows (clipping):
Top view of an already newly connected tunnel contour
The seven lines represent the cross section refinement, the centre line is the original l-structure.
Vertical section of the completed tunnel:
Vertical section of the completed tunnel