Narrow Vein Stope Design
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Transcript Narrow Vein Stope Design
Narrow Vein Stope
Design
Penny Stewart
PhD BEng(Mining)
Evaluate Previous Methods
Empirical Stability graphs
Industry standard.
Developed from 100’s of large open stoping case studies with few narrow-vein case
studies in database.
~ 80% accurate when applied to large open stopes.
Stopes designed using stability graphs would expect between 5-10% dilution.
1 0 0 0 .0 0 0
STABLE
1 0 0 .0 0 0
S ta b ility N u m b e r, N
F A IL U R E
1 0 .0 0 0
1 .0 0 0
0 .1 0 0
STABLE
F A IL U R E
0 .0 1 0
M A J O R F A IL U R E
S -F B o u n d a ry
0 .0 0 1
1
10
100
S h a p e F a c to r, S
Extended Mathews Stability Graph, after Mawdesley and Trueman, 2000
Applicability to Narrow-vein
677 relatively narrow case studies from Barkers mine (WA), Callinan
mine (Canada) and Trout Lake mine (Canada) showed poor correlation
to existing stability graphs.
Application of existing stability graphs to narrow-vein is problematic
because they do not take into account:
Relaxation
Blasting parameters
Stress damage
Backfill abutments
These parameters were shown to significantly affect
narrow-vein dilution
Adjustments for each of these effects
Stress Relaxation Study
Hypothesis: Due to their tabular geometry,
narrow-vein stopes are particularly susceptible
to relaxation.
Literature on effect of stress relaxation was
conflicting and contradictory.
Theorised that different types of stress
relaxation behave differently. 3 types defined:
Partial relaxation
Tangential relaxation
Full relaxation
Empirical study 55 case studies using Map3d
Results – Full and tangential relaxation required
adjustments
- 30% reduction in stability number, N.
Stress Damage Study
Hypothesis: Stress damage contributes to narrow-vein
dilution.
Stope walls exposed to high stress.
Results of Stress Damage Study
Of 410 case studies modelled over 36 months of mine life, only
10 incurred stress damage related dilution.
Stress damaged stopes had 0.27 m more overbreak than nonstress damaged stopes (94% confidence level)
0.27 m overbreak = 34% dilution
140
120
Stress (MPa)
100
80
60
40
20
0
Jun-00
Oct-00
Jan-01
Apr-01
Jul-01
Nov-01
Feb-02
May-02
-20
Normal Stress
Maximum Shear Stress
Sep-02
Dec-02
Mar-03