5
nyeld =2
nelcf =193152
nsol =2
nprb =6
mgob =0
error= 1.0000
orf =1.8600
xfac =56.7273
yfac =56.7273
zfac =12.0000
efac =1.0000
cfac =1.0000
tolr% =0.0100
ENDRUN
A conjugate gradient solver is used (nsol=2), although
Gauss Seidel iteration is also available (nsole=0). Run times
were approximately 11.5 hours which allows for overnight
turn around on a 64-bit word length PC. The simple three
step process allows for efficient redesign and avoids costly
errors in the field.
Figure 8 is a comparison of results in the form of ele-
ment safety factor distributions (fs=”strength”/”stress”)
where suitable three-dimensional measures of strength and
stress are d. Results in Figure 8 (A) are from use of labora-
tory rock properties and in Figure 8 (B) from use of jointed
rock mass properties. Both are at the Trona 1 level, the
mining horizon, corresponding to Figure 7. These results
show that joints do matter, but the shaft is safe at the min-
ing horizon. Small elements near the shaft wall allow for
accurate computation of stress concentration while larger
elements away from the shaft wall allow for efficient com-
putation overall.
The element safety factors near the shaft wall are 2.7
according to the color code and indicate a safe, stable
excavation in case of laboratory rock properties. In case of
jointed rock properties, the shaft wall elements show safety
factors in the red, 1.4, and indicate a likely need for some
surface support. In fact, a concrete liner was provided. This
liner was 1 ft (0.3 m) thick in the upper portion of the shaft
and 2 ft (0.6 m) thick in in the lower portion.
Figure 9 shows a comparison of element safety factor
distributions in the first element layer of Oil Shale 8 that
forms the bottom of the shaft. Element yielding is evident
at the shaft wall where stress concentration is relatively
high, but the extent is only through the first ring of ele-
ments and would not pose a threat to shaft safety.
Figure 10 shows the distribution of element safety fac-
tors in a vertical section after complete shaft excavation.
Safety factors decrease with depth but do not indicate a
threat to shaft safety or stability.
Figure 8. Element safety factor distributions at the mining
horizon (Figure 5) using laboratory rock properties (A) and
jointed rock properties (B) after excavating 500 ft upwards
from the mining horizon. Gray elements are excavated
shaft diameter is 26 ft (7.9 m). Black circles are safety factor
contours at an interval of 0.5
nyeld =2
nelcf =193152
nsol =2
nprb =6
mgob =0
error= 1.0000
orf =1.8600
xfac =56.7273
yfac =56.7273
zfac =12.0000
efac =1.0000
cfac =1.0000
tolr% =0.0100
ENDRUN
A conjugate gradient solver is used (nsol=2), although
Gauss Seidel iteration is also available (nsole=0). Run times
were approximately 11.5 hours which allows for overnight
turn around on a 64-bit word length PC. The simple three
step process allows for efficient redesign and avoids costly
errors in the field.
Figure 8 is a comparison of results in the form of ele-
ment safety factor distributions (fs=”strength”/”stress”)
where suitable three-dimensional measures of strength and
stress are d. Results in Figure 8 (A) are from use of labora-
tory rock properties and in Figure 8 (B) from use of jointed
rock mass properties. Both are at the Trona 1 level, the
mining horizon, corresponding to Figure 7. These results
show that joints do matter, but the shaft is safe at the min-
ing horizon. Small elements near the shaft wall allow for
accurate computation of stress concentration while larger
elements away from the shaft wall allow for efficient com-
putation overall.
The element safety factors near the shaft wall are 2.7
according to the color code and indicate a safe, stable
excavation in case of laboratory rock properties. In case of
jointed rock properties, the shaft wall elements show safety
factors in the red, 1.4, and indicate a likely need for some
surface support. In fact, a concrete liner was provided. This
liner was 1 ft (0.3 m) thick in the upper portion of the shaft
and 2 ft (0.6 m) thick in in the lower portion.
Figure 9 shows a comparison of element safety factor
distributions in the first element layer of Oil Shale 8 that
forms the bottom of the shaft. Element yielding is evident
at the shaft wall where stress concentration is relatively
high, but the extent is only through the first ring of ele-
ments and would not pose a threat to shaft safety.
Figure 10 shows the distribution of element safety fac-
tors in a vertical section after complete shaft excavation.
Safety factors decrease with depth but do not indicate a
threat to shaft safety or stability.
Figure 8. Element safety factor distributions at the mining
horizon (Figure 5) using laboratory rock properties (A) and
jointed rock properties (B) after excavating 500 ft upwards
from the mining horizon. Gray elements are excavated
shaft diameter is 26 ft (7.9 m). Black circles are safety factor
contours at an interval of 0.5