Download Map3D User`s Manual

Model Building and Editing
49
DOR controls the maximum element aspect ratio. If the ratio of the side length of an element is
determined to exceed DOR, that element is subdivided. The recommended value of DOR is 5. If
erratic results are detected, DOR should be decreased to 2. Note that smaller values of DOR results
in more elements and longer run times, but greater accuracy.
During discretization, Map3D will attempt to satisfy the specified DOR ratio for all elements. When
discretizing, the maximum number of boundary elements that any block or plate edge can be
divided into is 256. If this number of subdivisions is reached, and the specified DOR ratio has still
not been achieved, Map3D will issue a warning message instructing the user to subdivide the block
or plate into smaller pieces.
DOC - Matrix Lumping
During matrix assembly, the distance Delem between groups of Blocks and DD planes is examined
to see if these can be lumped together for calculation and storage purposes. The amount of lumping
depends on how many elements can fit into a zone with side length Lelem, determined from the
relation
Lelem = Delem/DOC
A value for DOC of 1.0 is recommended for all problems except those where increased accuracy is
required. With a value of 1.0 an error of 10-20% can be expected. A value of 2.0 should provide 510% error. A value of 4.0 should provide less than 5% error.
Although higher values of DOC result in larger problem sizes, this is necessary to obtain increased
accuracy.
Lelem
Delem
DOC controls the way in which elements are lumped during matrix assembly. Elements with
combined side length Lelem, are lumped if the distance Delem, to the affected element exceeds the
required DOC ratio. If the stope to stope distances are large, many elements can be lumped.
Small values of DOC (one or less) will provide maximum lumping, however, stresses near excavation
surfaces will deteriorate in accuracy, and matrix conditioning will be reduced. Larger values of DOC
(two or more) will provide less lumping, but accuracy and good matrix conditioning will be
maintained.
DOC should be set to 1 for coarse analysis results, 2 for detailed analysis results, and 4 when very
high accuracy is required. Note that large values of DOC results in increased matrix size and longer
run times, but greater accuracy.
DOE - Element Lumping
During the calculation of field points (i.e. grid assembly), the distance Dgrid between these points
and groups of Blocks and DD planes is examined to see if these groups can be lumped together for
calculation purposes. The amount of lumping depends on how many elements can fit into a zone
with side length Lgrid, determined from the relation
Lgrid = Dgrid/DOE
A value for DOE of 2.0 is recommended for all problems except those where increased accuracy is
Map3D International Ltd 1990-2015