In the PLAXIS 3D AE version, it is not directly possible to intersect lines with surfaces. This is because of the parametric definition of the PLAXIS 3D AE surface objects, which is not compatible yet for line objects.
This makes the process of designing rock bolts for a tunnel project cumbersome since the created lines might not be accurately snapped on the lining (surface) of the tunnel. The manual snapping of the endpoint to the tunnel lining can be done, however, this might change the angle of the rock bolt slightly, which may be undesired. A manual intersection of the line and surface could solve the problem. However, this is not currently possible.
Depending on the desired geometry, different approaches are suggested. In this article the following cases are explained, related to the reference point that is given for designing the rock bolts:
In this case, the reference point is located inside the tunnel geometry. This point and a given angle assists in providing the direction of the rock bolt.The following steps describe how to create a rock bolt accurately snapped on the surface of the tunnel lining:
For this example the following assumptions are taken:
point (25 1 -20) # reference point
lineangles Point_1 0 60 Surface_2 # line under 60 degree angle extended to Surface_2
delete Lines[-1] # optional
lineangles Points[-1] 0 60 4 # same command with length
embeddedbeam Lines[-1] "Behaviour" "Rockbolt" "ConnectionPoint" "First"
In this case, the suggested alternatives are given below using two available commands: lineangles and the line command using "vector" parameters.
The following steps describe how to create a rock bolt accurately snapped on the surface of the tunnel lining:create the reference point
point (32 1 -7.5) # reference point
lineangles Point_1 0 240 Surface_2 # adjust angle
line command with "vector" parameters
The line command can be used in different ways. One way to create a line is by using a vector to define the direction of the line towards a surface. The structure of this command is the following:
line | reference point (x,y,z) | "vector" | direction (a,b,c) | target object
line 2 5 0.2 "vector" 0 -1 0 Surface_1
Creates a line from a new point with coordinates (2, 5, 0.2) with a direction of (0, -1, 0) onto Surface_1.
The following steps describe how to create a rock bolt accurately snapped on the surface of the tunnel wall:
line 32 1 -7.5 "vector" -0.5 0 -0.866 Surface_2
embeddedbeam Lines[-1] "Behaviour" "Rockbolt" "ConnectionPoint" "Second"
( vector is calculated based on the following: [-0.5, 0, -0.866] = [cos60 , cos0 , cos30] )
These commands can also be written in a single line so it can easily be used when the rock bolt generation is prepared in, for instance, a spreadsheet program (see example here [link]). The (single line) command would look like this:
embeddedbeam (32 1 -7.5) "vector" -0.5 0 -0.866 Surface_2 "Behaviour" "Rockbolt" "ConnectionPoint" "Second" "Material" RockboltBeamMaterial
For more information on the structure of the commands used, please check the Command reference, under the Help menu in Input.
Using Rockbolts in the 3D Tunnel Designer
Command line reference
[Tips and Tricks]