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