CAD > Build > FFLoop
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Builds fully three-dimensional FF (Fictitious Force) type blocks. These are used for 3D excavations, alternate material zones (ore zones or dykes) and backfilled zones. The block surfaces will be further subdivided into boundary elements at a later stage in the program. In Map3D Non-Linear these zones can yield and behave non-linearly.
A few examples demonstrating this routine can be found under Model Building Tutorials. Refer specifically to
FFLoops
When the routine is initiated the user is prompted to select the corners that define the perimeter of a series of floor plans or sections. The direction you traverse each loop is not relevant. As many loops as desired can be defined simultaneously. The number of points does not have to be the same on each loop. The starting and end points on each loop (e.g. points 1 and 11 on the first loop, and points 12 and 22 on the second) must be at the same location to define a series of closed loops.
Trace
These points can be selected one at a time, or all points along a construction line segment can be selected using the
Close
The FFLoop routine is considered to be complete when one of the following two conditions is met:
•the user selects the final loop point (i.e. point #22) a third time
The loops will then be subdivided into a series of 3 or 4 sided FF elements. These surfaces will be further subdivided into boundary elements at a later stage in the program. The routine that does this subdivision searches for corners that are near one another, so the user should take care to define the loop such that the connections are straightforward. In the above example it is recommended that points 4 and 5 be selected or generated.
Guide Lines
For more complex shapes, guide lines (shown in yellow) can be defined, that force the sides to be subdivided along these lines. These are simply defined as construction lines. For an example refer to https://www.map3d.com/ffloop.htm. Guide lines must not intersect or cross one another.
Extrusion using Offset
Once the first closed loop has been entered, the remaining points can be generated by offsetting the remaining points using
Miscellaneous
The coordinates of the corners can be typed in from the keyboard
selected by freehand drawing, picked from other entities (other blocks or construction lines) or digitized
A large variety of drawing tools are available to assist in visually selecting points from the model
Corners can be unselected using
Corners can be reselected using
Upon completion of block construction the user is prompted to enter the block properties. This allows you to specify the various parameters including the block colour and mining sequence.
Block Volume - displays the volume of the block.
Block Name - specifies a descriptive name for the block.
Element Type - specifies the type of boundary element that will be used for the block.
•Fictitious Force - FF elements should be used for three-dimensional features such as excavations, alternate material zones, back-filled stopes etc. •Displacement Discontinuity - DD elements should be used for tabular mining excavations, fractures and fault planes. •Inactive elements can be used to display features that are to be included for visualization purposes only and not to be used for the actual stress analysis.
Block Colour - specifies the colour number that will be used to display the block.
Specifies the colour number that will be assigned to each button. A total of 10 colours are available for display. These are numbered respectively
1 through 10, 11 through 20, 21 through 30, etc.,
such that the same colour is displayed for numbers
1, 11, 21..., 2, 22, 32..., 3, 23, 33..., etc.
Fixed Element Width - specifies the user defined element width.
This parameter can be used to force uniform discretization on selected entities. Extreme caution should be used in specifying this value since a small value can easily lead to enormous problem size.
In general this option should not be used (unchecked) and discretization should be left to the AL and AG parameters. These latter parameters will concentrate elements only where analysis results are requested thus optimizing the use of elements and minimizing problem size. For further discussion refer to
CAD > Properties Control Parameters
This parameter can also be used to avoid making surfaces with sides larger than this during the intersection analysis. Any surfaces whose side length exceeds this dimension will not be collapsed
During the discretization process, any surface whose side length exceeds this dimension will be subdivided to prevent surfaces having sides larger than this.
For an example of the use of this parameter refer to Tabular Mining Example
Matl_Code LERD/MStep - specifies the material code that will be substituted into the block for the LERD/LSS calculation.
The first box is for the material code. The second box is to specify the mining step number when the calculation is to be done. If this box is left blank then the LERD calculation will be done for all steps.
Analysis > Options > LERD/LSS.
Mining Step n - specifies the material code that will be used for this block in mining step n. In the above example, the block is non-existent at step 1, has material #2 (Ore) inserted in it at step 2, it is excavated at step 3 (material code 0 means to excavate), and finally at step 4 material #5 (backfill) is inserted. When you use a positive material number, the material is placed into the block at the specified initial stress state, and is then allowed to deform according to the elastic/plastic properties you have set for that material number. When you use a negative material number, the material is placed into the block at the specified initial stress state, but the stress state is held at these vales regardless of the deformations, thereby providing a stress boundary condition.
Generate Separate Loop Blocks - if you are building multi-loop blocks, you can specify whether or not interfaces will be created between each block so that each block can be treated as a separate mining unit. If you do not specify this option then a single large block will be created.
Offset - allows you to offset a planar loop to extrude the block into a 3D shape. This operation can also be done using Extrude/Offset Remaining.
More Steps - allows specification of additional mining steps.
Clear All Steps - clears all mining steps (1-100).
Undo - unselects the last point entered and returns to the block construction routine
Copy From… - allows you to select another block to copy the entity properties from.
Mesh - builds the block with surfaces subdivided into smaller parts at the specified block grid spacing.
Build - completes block construction and enters the block into the model database.
Once you have completed this operation you have one last chance to undo this and remove this block from the model database by selecting
Cancel aborts block construction.
Note that it is possible to create zero volume blocks for example by specifying a zero length offset vector. This allows users to construct individual FF surfaces if desired. While this is permissible it is not recommended as this can lead to unclosed volumes.
FF blocks can be collapsed into DD planes at any time simply by changing the element type
In this case the base of the block (the side defined by corners 1, 2, 3 and 4) will become the DD plane and the remainder of the block sides will be discarded.
Notes:
Different colour numbers should be used to represent logical groupings of blocks (e.g. for different levels, sections or logical mining units such as development, stoping etc.). These colours are user definable
Any blocks with the same colour number will be automatically combined into single complex shapes by Map3D.
Since it is easy to toggle on and off the display of specific block colour numbers
This provides an efficient method to work with complex model data.
For discussion on model building aspects refer to:
For tutorials on model building refer to:
Pressing the space-bar automatically activates the last build function that was used. |
