8
than the base case of the larger, defaults ramp radius case,
although a visual comparison toes not indicate much dif-
ference. The number of 360 deg loops in the spiral can be
varied also.
CONCLUSION
Mine ramps are important features of many underground
mines but are not easy to design because of ramp geom-
etry and geology. However, software specially formulated
to accommodate ramp complexity makes design as easy
as one-two-three. The first and most difficult step is the
specification of rock formation and joint set properties in
the region of interest. Elastic moduli, strengths, formation
depths, thicknesses, and directions are needed and joint
set properties, as well. The second step is mesh generation
and is done interactively with specification of ramp section
shape, ramp type (zig-zag, spiral), starting depth and grade.
Mesh plotting is also easy once generated and allows for
visual checking. A finite element runstream file is gener-
ated during this second step. The third step is execution
occur at the corners near the section bottoms and over the
section shoulders where stress concentration is expected to
be relatively high. Bolting and screening are indicated in
this case. However, element safety factors increase rapidly
with distance into the solid (indicated by color change from
red to green and blue).
Ramp radius is set at a default value of 11.25 times
opening width but can changed during mesh generation.
There is no default ramp grade, but is also set during mesh
generation.
Figure 9 shows the distribution of element safety fac-
tors in case of the ramp radius set at one-half the default
value. In this case, approximately 4.8% of the elements have
yielded. Thus, element failures are one-third more than the
base case of the larger, defaults ramp radius case, although a
visual comparison toes not indicate much difference.
Figure 10 shows the distribution of element safety fac-
tors in case of the ramp radius set at the minimum value of
mesh width. In this case, approximately 5.2% of the ele-
ments have yielded. Thus, element failures are 44% more
Figure 9. Element safety factor distributions in cross-sections of a 360 deg spiral ramp at one-half the default ramp radius
than the base case of the larger, defaults ramp radius case,
although a visual comparison toes not indicate much dif-
ference. The number of 360 deg loops in the spiral can be
varied also.
CONCLUSION
Mine ramps are important features of many underground
mines but are not easy to design because of ramp geom-
etry and geology. However, software specially formulated
to accommodate ramp complexity makes design as easy
as one-two-three. The first and most difficult step is the
specification of rock formation and joint set properties in
the region of interest. Elastic moduli, strengths, formation
depths, thicknesses, and directions are needed and joint
set properties, as well. The second step is mesh generation
and is done interactively with specification of ramp section
shape, ramp type (zig-zag, spiral), starting depth and grade.
Mesh plotting is also easy once generated and allows for
visual checking. A finite element runstream file is gener-
ated during this second step. The third step is execution
occur at the corners near the section bottoms and over the
section shoulders where stress concentration is expected to
be relatively high. Bolting and screening are indicated in
this case. However, element safety factors increase rapidly
with distance into the solid (indicated by color change from
red to green and blue).
Ramp radius is set at a default value of 11.25 times
opening width but can changed during mesh generation.
There is no default ramp grade, but is also set during mesh
generation.
Figure 9 shows the distribution of element safety fac-
tors in case of the ramp radius set at one-half the default
value. In this case, approximately 4.8% of the elements have
yielded. Thus, element failures are one-third more than the
base case of the larger, defaults ramp radius case, although a
visual comparison toes not indicate much difference.
Figure 10 shows the distribution of element safety fac-
tors in case of the ramp radius set at the minimum value of
mesh width. In this case, approximately 5.2% of the ele-
ments have yielded. Thus, element failures are 44% more
Figure 9. Element safety factor distributions in cross-sections of a 360 deg spiral ramp at one-half the default ramp radius