Evolution of Panel Caving in Primary Ore

Authors: Cesar Pardo
Eduardo Rojas
May 2016
Selection of Exploitation Method
Based on the Experience of
Hydraulic Fracture Techniques at
the El Teniente Mine
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Content
• El Teniente Overview
• Lessons Learned from Exploitation of Primary Ore
• Evolution of Panel Caving in Primary Ore
• Reflections
2
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Overview
Codelco Chile - El Teniente Division
3

The biggest underground copper mine
in the world, in operation since 1905.

More than 110 million tonnes of copper
in geological resources, and 36 million
tonnes of copper in ore reserves.

Current Production Rate: 140 ktpd

An integrated complex: Mine - Plant Smelter facilities.
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Overview
El Teniente Mine Isometric view

Abrupt topography (more than
1km difference between the
lowest and highest part of the
mountain).

Influence of tectonic
4
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Overview
El Teniente Mine - Geology
3700 msl
Crater
Quebrada Teniente
Level 1983 (Ten-8)
1° - 2° contacto
Dacita
Level 1500m
Level 1200m
Braden Pipe
N
5
Tonalita
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Overview
El Teniente Mine - Geology
Brecha Braden
Stockwork Andesita Hw (Esmeralda Mine)
6
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
RQD= 90-100

GSI= 80-100

UCS= 120-150
1
Overview
El Teniente Mine – Premining Stress
3
7
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Lessons Learned from Exploitation of
Primary Ore
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Lessons Learned from Exploitation of Primary Ore
Hidrofracturing concept
9
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Lessons Learned from Explotation of Primary Ore
Hydraulic fracture features and its conceptualisation
The HF is formed in the major and
intermediate principal stress plane.
Circular shape assumed for design
purpose (20m radius after a 30 min)
Tensile Failure mode
HF spacing 1.5m.
10
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Lessons Learned from Exploitation of Primary Ore
Results of Implementation Hidrofracturing
11
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Lessons Learned from Exploitation of Primary Ore
Results of Implementation Hidrofracturing
Polígono de control RENO
Sobr
Polígono de control RENO
Maximum Events Magnitude vs. Extraction Rates
40
PA RENO
Columna
3.20
35
15 m
30
2.40
25
E
v
e
n
t
K
T
20
P
D
M
a
g
n
i
t
u
0.80
d
e
1.60
15
10
60 m
60 m
0.00
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
Year
Extraction Rates
12
Max Magnitude 60<UCL<100
Max Magnitude HF above UCL (up to 100m)
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Colu
P
100 mm
100
Elevation 2120
UCL 2120 msnm.
Elevation 2102
Bajo
NP 2102 msnm.
Elevation 2120
UCL 2120 msnm.
Elevation 2102
Bajo
NP 2102 msnm.
60 m
5
0
Colu
P
100 mm
100
15 m
60 m
2000
Sobr
PA RENO
Columna
PA Ba
Fal
PA RENO
Falla G
PA RENO
Elevation 2064
Falla G ACARREO 2064 msnm.
Elevation 2064
ACARREO 2064 msnm.
PA Ba
Fal
Lessons Learned from Exploitation of Primary Ore
Evolution of ground support system
Estallidos de Rocas v/s Producción años 1982 a 2015
70
Bolts L
Plate
Welded Mesh
Shotcrete2 Kj/m2
125
Rhomboid mesh
60
>12 Kj/m2
KTPD
50
Bolt  25 mm
100
Face support
Chainlink mesh
5 Kj/m2
Cablebolting
75
40
Second pass mesh
30
50
Reduction shotcrete
thickner over the
mesh
Mesh to
the face
25
10
Producción Primario
Pilar Norte
Ten-3 Isla Martillo
Isla LHD
Esmeralda
Ten Sub-6
13
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Ten-4 Sur
2015
2014
2013
2012
2011
2010
2009
2008
2007
2006
2005
2004
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
1991
1990
1989
1988
1987
1986
1985
1984
1983
0
1982
0
20
AMJ
# Estallidos de Rocas
150
Lessons Learned from Exploitation of Primary Ore
Evolution of Drawpoint support
Stiffener plates
14
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Evolution of Panel Caving in Primary Ore
15
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Evolution of Panel Caving in Primary Ore
Panel Caving, Post Undercutting sequence (1982 -2010)
•
One or two drawbell ahead of the
undercut front. Blast undercut on top
of the drawbell.
Factor Intensidad Abutment Stress
FI = abutment / in-situ
>4
3-4
<3
•
The abutment stresses affected the
crown pillar with a medium to high
intensity factor. Impacting on the
drawbell incorporation.
Frente
Hundimiento
NH
NP
16
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Evolution of Panel Caving in Primary Ore
Panel Caving, Post Undercutting sequence (1982 -2010)
The productive area availability was about 50% (mainly due to orepass damage and
rorkburst and collapses afecting the extraction level). Drawpoints rehabilitation reached
up to 25%.
Damage at Drawpoint
17
Damage
at
Ore
pass
(production: 350.000 ton)
Collapses T4 SUR
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Evolution of Panel Caving in Primary Ore
Panel Caving, Pre Undercutting sequence (1997 -2005)
•
Undercut a beam (Low and flat) of 60m long to
provide stress shadow to the extraction level.
•
Development of the extraction level drives and
drill and blast of the drawbells under the stress
shadow.
•
18
Frente
Extracción
Abutment stress zone ahead of the caving front
produced a very high intensity factor (over 4 ) on
the undercut level.
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Frente
Hundimiento
Abutment stress intensity factor
Undercut cantilever beam
Cantilever beam length (m)
19
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Remnant pillar
Drawpoint damage
Remnant pillars caused by loss of
changing holes- These remnant
pillars
transferred
load
to
extraction
level resulting in
collapses.
Lack of operational flexibility, i.e
Development is highly dependent
on undercut rate.
20
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Evolution of Panel Caving in Primary Ore
Panel Caving, Advanced Undercutting sequence (2004 -2014)
•
Undercut a beam (Low and flat) of 60m long to
provide stress shadow to the extraction level.
•
Development of the extraction level drives
independent of the undercut front.
•
Drawpoint connection and drawbells construction
under the stress shadow.
•
Abutment stress zone ahead of the caving front
produced a very high intensity factor (over 4 ) on the
undercut level.
•
21
Similar issues experienced in the pre undercut
variant
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NP
Evolution of Panel Caving in Primary Ore
Panel Caving, Post Undercutting with HF (2010 -2015)
•
•
Rock mass preconditioning by hydraulic
fracturing ahead of the undercut front (>=100).
Fracturas FH
One or two drawbell ahead of the undercut
front. Blast undercut on top of the drawbell.
Pozo FH
•
The abutment stresses affected the crown pillar
with a medium to high intensity factor.
Impacting on the drawbell incorporation.
Fracturas FH
Pozo FH
Post Undercut with FH
22
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Case example: Esmeralda
100m bajo UCL y 170m
Sobre UCL
23
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Case example: Esmeralda - Seismic response
(a) Esmeralda Tradicional: Hundimiento Previo sin FH
Socavación
(b)Esmeralda Bloque 1: Hundimiento Convencional con FH
Incorporación de bateas y socavación
2380
2380
Proceso de
conexión
2360
2340
2320
Magnitud < 0.9
Magnitud 1.0 – 1.5
Magnitud 1.6 – 1.9
Magnitud 2.0 – 2.5
Magnitud > 2.6
2320
2300
2280
2280
2260
2260
2240
2240
UCL
NP
2180
Acarreo
Acarreo
2160
Magnitud 1,0 a 1,5
Magnitud 1,6 a 1,9
Magnitud 2,0 a 2,5
Magnitud 2,6 a 2,9
Caving en Régimen
Magnitud 0,6 - 0,9
Magnitud 1 a 1,5
Section view: (a) Pre & advance undercut , (b) post undercut with HF.
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Magnitud 1,6 a 1,9
Magnitud 2,0 a 2,5
30-07-2014
30-06-2014
31-05-2014
01-05-2014
01-04-2014
02-03-2014
31-01-2014
01-01-2014
02-12-2013
02-11-2013
03-10-2013
03-09-2013
04-08-2013
05-07-2013
05-06-2013
06-05-2013
06-04-2013
07-03-2013
05-02-2013
06-01-2013
07-12-2012
07-11-2012
08-10-2012
08-09-2012
09-08-2012
10-07-2012
10-06-2012
11-05-2012
11-04-2012
12-03-2012
11-02-2012
12-01-2012
13-12-2011
13-11-2011
2120
14-10-2011
09-08-1995
08-10-1995
07-12-1995
05-02-1996
05-04-1996
04-06-1996
03-08-1996
02-10-1996
01-12-1996
30-01-1997
31-03-1997
30-05-1997
29-07-1997
27-09-1997
26-11-1997
25-01-1998
26-03-1998
25-05-1998
24-07-1998
22-09-1998
21-11-1998
20-01-1999
21-03-1999
20-05-1999
19-07-1999
17-09-1999
16-11-1999
15-01-2000
15-03-2000
14-05-2000
13-07-2000
11-09-2000
10-11-2000
09-01-2001
10-03-2001
09-05-2001
08-07-2001
06-09-2001
05-11-2001
04-01-2002
Magnitud 0,6 a 0,9
Inicio de Caving
2140
14-09-2011
Caving en Régimen
15-08-2011
Inicio de Caving
2120
16-07-2011
2140
2200
16-06-2011
2160
2220
17-05-2011
2180
UCL
NP
17-04-2011
2200
Magnitud < 0.9
Magnitud 1.0 – 1.5
Magnitud 1.6 – 1.9
Magnitud 2.0 – 2.5
Magnitud > 2.6
2340
2300
2220
Proceso de
conexión
2360
Case example: Esmeralda - Undercut drift damage
Advance undercut
25
Post undercut with HF
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Case example: T4 Sur - Esmeralda / drawpoint damage
Post Undecut (T 4 Sur)
26
Post Undercut with FH (Esmeralda)
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Global Results
Rock burst
Estallidos de Rocas v/s Producción años 1982 a Diciembre de 2015
150
70
Producción Primario
Pilar Norte
125
60
Ten-3 Isla Martillo
50
Esmeralda
100
KTPD
Ten Sub-6
Ten-4 Sur
40
75
30
50
20
25
N° Estallidos de Rocas
Isla LHD
10
2015
2014
2013
2012
2011
2010
2009
2008
2007
2006
2005
2004
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
1991
1990
1989
1988
1987
1986
1985
1984
1983
0
1982
0
AÑO
27
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Global Results
Collapses
Area Colapsada v/s Producción años 1982 a Diciembre de 2015
150
25
Producción Primario
Ten-4 Sur
20
Ten Sub-6
Esmeralda
100
Regimiento
KTPD
15
75
10
50
5
25
0
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
0
Area Colapsada (m2/1000)
125
AÑO
28
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Reflexions
The success of a mining method relies on a
robust design accompanied of a
implementation and operation stages
that follows the desing.
The mining method should be easily
implemented by the operators.
The engenineering stage should provide
clear rules to be followed during the
operation.
The mining method need to allow for
flexibility should change in geotechnical
conditions, technology and safety practices
occurs.
29
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Thank you
Questions?
30
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