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GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
EMPIRICAL DESIGN METHODS – UBC GEOMECHANICS
RESEARCH –CERM3 WORKSHOP
R. PAKALNIS - UBC
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
INTRODUCTION
• ANALYTICAL• OBSERVATIONAL
•EMPIRICAL
SAFETY & WORKABLE
INTRODUCTIONINTRODUCTION
• QUANTIFY ROCK MASSQUANTIFY ROCK MASS• RELATE TO PAST PRACTICERELATE TO PAST PRACTICE
• PREDICTIONPREDICTION
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
• STOPE DESIGN• PILLAR DESIGN• SPAN DESIGN
• SUPPORT
1998
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
STRESS
• INDUCED LOAD• INPUT PARAMETERS
• GUESTIMATE
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
STRUCTURE
• GEOMETRY• SHEAR STRENGTH
•SUPPORT
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
ROCK MASS CLASSIFICATION
• RMR (1976)•Q - SYSTEM (1974)
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
OPENING DESIGN
• STABILITY GRAPH (ELOS)• CRITICAL SPAN CURVE
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
ELOS – EQUIVALENT LINEAR OVERBREAK SLOUGH
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
PARALLEL STRUCTURE B = 0.2, 0.3
RELAXED HW A = 1
WALL DIP
C = ( 8 - 6*COS )
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
MODIFIED STABILITY GRAPH – RADIUS FACTOR
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
RADIUS FACTOR = 1.1 X HYDRAULIC RADIUS
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
OPENING DESIGN
• STABILITY GRAPH (ELOS)• CRITICAL SPAN CURVE
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
Updated Span Design Curve (292 obs)
Des
ign
Sp
an
(m
)
Rock Mass Rating
UNSTABLE
STABLE
Unstable Potentially Unstable
Stable
Span = Diameter of the largest circle which can be drawn between pillars and walls in plan view
SpanPost Pillar
Span
SPAN DESIGN CURVE
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
Updated Span Design Curve (292 obs)
Des
ign
Sp
an
(m
)
Rock Mass Rating
UNSTABLE
STABLE
Unstable Potentially Unstable
Stable
Span = Diameter of the largest circle which can be drawn between pillars and walls in plan view
SpanPost Pillar
Span
• WEAK ROCK MASS
• SEISMICITY
•EXTENT OF FAILURE
(5.5 2.5 2.5 5.5)
6ft
10ft
3ft x 3ft BOLT SPACING
(0.5*10ft*5ft*3ft)/11ft3/ton= 7ton
5ft
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
MINE APPLICATIONSSPAN ESTIMATION
NEURAL NETS USED TO ARRIVE AT A DESIGN CURVENOT SOLELY AS A PRECDICTIVE TOOL/ BLACK BOX
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
PREDICTIVE TOOLSPAN ESTIMATION
292 CASE HISTORIES
(160 STABLE, 59 POT, 73 UNSTABLE)
18 X 18 GRID - NEURAL OUTPUT (324
pts)
3
1
3
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
PREDICTIVE TOOLSPAN ESTIMATION
NEURAL NET RESULTS IN CONTOUR PLOT OF 1=.100% STABLE TO 3=100% UNSTABLE
TRAINING ERROR = 12%
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
PILLAR DESIGN
• PILLAR LOAD/UCS• PILLAR WIDTH/HEIGHT
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
PILLAR STABILITY GRAPH
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
• Wp/Hp < 1
• SEISMICITY
PILLAR STABILITY GRAPH
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
• 1700m below surface
• 47g/tonne GOLD
• 600 TPD
GOLDCORP RED LAKE MINE
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
STABLE UNSTABLE FAILEDLOW BURST POTENTIAL MEDIUM BURST POTENTIAL HIGH BURST POTENTIAL
Pillar Stability Graph FS>1.4 on Pillar Stability Graph 1.0 < FS < 1.4 FS<1.0
Induced Stress Criteria s 1/UCS < 0.5 0.5 < s 1/UCS < 0.6 s 1/UCS > 0.6
Pillar Geometry Wp/Hp > 3 2 < Wp/Hp < 3 Wp/Hp < 2
Observations Minor ground working, minor spalling Ground working, pillar spalling Substantial bursting *
* in process of being evaluated - microseismic
BURST PRONE CRITERIA
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
STUDY AT QUINSAM MINE – BRITISH COLUMBIA - CANADA
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
SURFACE SUBSIDENCE OVER SHALLOW EXCAVATIONS
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
• ANGLE OF CRITICAL DEFORMATION IS <10o FROM VERTICAL
• STRUCTURAL CONTROL
• DEPTH OF CAVE AS MUCH AS 14X EXCAVATION HEIGHT
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
CONCLUSIONS
CALIBRATION TO ANALYTICAL AND EMPIRICAL APPROACHES
MODIFIED ACCORDING TO MINE BEHAVIOUR
SAFETY & WORKABLE
INTERPOLATE, NOT EXTRAPOLATE
KNOW THY DATABASE TOOL
GEOMECHANICS DESIGN GROUP
UB
C M
ININ
G &
MIN
ER
AL P
RO
CES
S E
NG
INEER
ING
ACKNOWLEDGEMENT
NIOSH
CERM3