Procedures for wireframe modelling of tectonic faults in Datamine Studio3
Preface.
Very often hand made drawings are the only source for the structural analyses of
the deposit. At the same time, they represent an excellent and cheap option for
building a structural model. Though, since they come from the "2D" era, their value
for 3D modelling depends on how accurate is their geometry (coordinates, orientation.
elevations, etc.)
There is a wide choice of digitizing software available. I leave it up
to the user to choose the program providing that scaling and positioning of the image in the CAD window
is as much accurate and precise as possible.
It is important to make sure the digitized line is "flat" (that is, series of vertex points of a line
have one and the same elevation) and in XY plane of WCS or parallel to it.
.
If this condition is not met, that is the line you draw is 3D,
horizontal projection of the intersection line of the 3D fault and the surface wireframe
will not coinside with the digitized line.
Also, make sure the line is has the elevation
above the highest point of the terrain.
For digitization I consider using AutoCAD
poly-line objects with provides the equal elevation vertices as default. Though, users may prefer other software, but
requirements for the above mentioned line attributes are important.
Assuming you are familiar with Studio 3/RM at a beginner's level, such as you can
create a project file, add files to the project, import and export objects,
understand peculiarities of activating function with key combination
and typing command into the command line, etc.,
this exercise would
not be difficult to follow.
Project 2D perimeters to 3D perimeters in wireframe DTM surface
A line drawn on paper is "a priori" projection of a 3D string on a plane of
a table top on which the paper is placed. So is the fault line, indicated by red arrows on the
picture below.
From the draftsman's point of view, this is an intersection of a fault plane
with the terrain surface, but with pencil and paper he can only draw a flat
line.
The digitized string will look like a flat curve above or below the surface, depending on the elevation of the plane which it was drawn on.
What we should do is to project the line on the surface orthogonally
(at 90 degrees) to get the 3D projection of the line. To do this, Datamine Studio
offers a command PERDTM, which must be entered into the command line.
Pick up or enter the digitized string name, which you are going to project
on the surface in the PERIMIN* cell. Do the same for the surface files: WIREPT*
and WIRETR*.
Enter a name for the output file in PERIMOUT*. Press OK.
Visualizer window shows digitized string (red) and orthogonal projection (yellow)
of it on the surface
SETTING FACE ANGLE
Face Angle is a function from the Open-Pit Module for controlling bench and overall slope angles,
and can successfully be used in our example.
Go to Applications | Open Pit | Set Face Angle.
In this example, the fault is deeping 72 degrees to the NE. Remember the deep
angle is the angle between horizontal plane and the fault plane at the measurement point.
Enter the angle and press OK.
PROJECTING STRINGS ON PLANE.
We need to project the 3D string on a plane below the surface at the fault deep angle
of 72 degrees. From visualization point of view it may be useful to extend the fault plane
at some height above the surface.
Tun off all objects, except the 3d string faultsplST in the Sheets tab
on the left of Design window. Click on the line (select object by clicking on it)
to make it active. It will turn yellow.
Click anywhere on the empty space in Design window to deactivate any previously
leftover commands.
Then click on the string to make it activate. It will turn yellow.
Type pro.
Type D for Down. Press OK.
Type 1900 as the Target Elevation of the plane you wish to extend the fault to.
Press OK.
Back in Design window, click near the selected line on the left side. A new
string will appear on the right.
Though the fault boundary with terrain is the intersection line, you should extend the imaginary part
of the fault
above the surface up in the air to provide enough fault face portion for
intersection with the terrain. Select the
3D string again by clicking on it, type pro, and in the appeared dialogue
type u in Projection cell, press OK, Type 2800 in Target Elevation
cell, press OK.
Before saving, check the strings for crossovers and fix them with string tools
if needed.
Now we have an upper and lower projection of a 3D string, which will be
used for wireframing
Visualizer view of all stings
WIREFRAMING
Use Wireframes | Linking | Link Strings command
(or type ls) to link upper and lower projection
strings. The resulting pictures below.
