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Building 3D Wireframes of Techtonic Faults

Tukhmanuk, Armenia

Procedures for wireframe modelling of techtonic 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 the structural model. Though, since they come from the "2D" era, their value for 3D modelling depends on how accurate is the survey data (coordinates, orientation. elevations, etc.) Nowadays there is a wide choice of digitizing software available. I leave it up to the user providing that scaling and positioning of the image in the CAD window is accurate and precise as much as possible.

It is important to make sure that the digitized line is "flat" (that is, every vertex has one and the same elevation). Also, make sure the line is given the elevation above the highest point of the terrain. For digitization I consider using AutoCAD poly-line objects. Though, users may prefer other software, but requirements for the above mentioned line attributes are important.

Assuming you are familiar with Studio 3 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.

Preloads

3D wireframe of a terrain in *.dm format; topoWf.7z
Digitized contour of the fault (2D poly-line) in *.dm format; fault-string2D.7z
Orthogonal projection of the digitized fault line on the terrain, in *.dm format; fault-perdtm.7z
Projected at 72d angle strings in *.dm format; up-down.7z
3D Wireframe of the fault in *.dm format; fault-WF.7z

Project 2D perimeters to 3D perimeters in wireframe DTM surface

A line drawn by a human on paper is "a priori" projection of any 3D string on a plane of a table on which the paper is placed. So is the fault line, indicated by red arrows on the picture below.

Tukhmanuk, Armenia

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.

When we download the digitized string, it will look like a curve somewhere in the air above or below the surface, depending on the elevation we give to it.

perdtm

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, the program offers a command PERDTM, which must be entered into the command line.

perdtm

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*. Choose a name for output file in PERIMOUT*. Press OK.

Visualizer window shows digitized string (red) and orthogonal projection (yellow) of it on the surface

perdtm

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.

perdtm

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.

perdtm

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.

perdtm

Type pro.

perdtm

Type D for Down. Press OK.

perdtm

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.

perdtm

If you wish to extend the fault above the surface up in the air, 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

perdtm

Visualizer view of all stings

perdtm

WIREFRAMING

Use Wireframes | Linking | Link Strings command (or type ls) to link upper and lower projection strings. The resulting pictures below.

perdtm

perdtm

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