metodologia del shotcrete
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Proposed Design
Methodology for shotcrete
W.C Joughin, G.C. Howell, A.R.
Leach & J. Thompson
-
Research Workshop Team
William Joughin
Graham Howell
Tony Leach
Jody Thompson
Kevin Le Bron
Karl Akermann (AngloPlatinum), Lars Hage (BASF), Alan Naismith, Julian Venter, Dave Ortlepp
-
Design Process
Determination of rock
mass and loading
conditions Rock mass classification Stress modelling
Determination of Shotcrete
Requirements Excavation requirements Shotcrete function/purpose Is it required?
Determination of
Shotcrete Demand Deadweight loading Quasi-static loading Dynamic loading
Determination of
Shotcrete Capacity Peak/Residual capacity Energy absorption Standard tests Fibre content, mesh characteristics
Determination
of safety factor
-
Rock mass conditions Q/GSI
Stress modelling
Low Stress Moderate stress High Stress Dynamic
Loading Condition
Ma
ssiv
e (>
70
)Jo
inte
d (4
0-7
0)H
eav
ily jo
inte
d (0.7, 1/c ratio)
Empirical charts (joint controlled + SRF)
-
Shotcrete requirements
-
Shotcrete requirements
-
Shotcrete Demand
Deadweight
Quasi-static
Dynamic
-
Shotcrete Demand
(deadweight)
Roof prism (Barret & McCreath)
Sidewall prism slides
Conservative estimate
-
0.1
1
10
100
0 1 2 3 4 5 6
md
(kN
m/m
)
Span between tendons (m)
20 kN/m3
25kN/m3
30 kN/m3
35kN/m3
40 kN/m3
Shotcrete Demand
(Deadweight)
-
Shotcrete Demand (quasi-static) Assumption: Rock mass will continue to deform
under quasi-static loading. Support pressures
provided by shotcrete are inadequate to prevent
deformation.
Objective is to survive the deformation and maintain the functions of containing the fractured
rock mass
If the moment demand exceeds the peak moment capacity, the shotcrete will enter the residual
state, providing it is reinforced.
-
Shotcrete Demand (quasi-static)
(Displacement) Displacement monitoring (extensometers)
Maximum displacement from Udec GRC modelling
-
0.E+00
1.E+05
2.E+05
3.E+05
4.E+05
5.E+05
6.E+05
7.E+05
8.E+05
9.E+05
1.E+06
0.00 5.00 10.00 15.00 20.00 25.00 30.00
Deformation (mm)
Su
pp
ort
Pre
ssu
re (
Pa)
300 MPa
250 MPa
200 MPa
150 MPa
Displacement from modelling
-
Shotcrete Demand (quasi-static)
(Displacement)
Quartzite150-200MPa 200-250MPa 250-300MPa
20 48.20 Squeezing Squeezing
30 5.50 Squeezing Squeezing
40 4.50 43.00 51.00
50 8.00 25.30 35.70
60 7.50 6.70 7.80
70 4.00 5.50 5.50
80 4.00 3.50 4.00
90 2.75 1.30 4.60
-
1.E-02
1.E-01
1.E+00
1.E+01
1.E+02
1.E+03
1.E+04
1.E+05
0 1 10 100 1,000
md
(kN
m/m
)
Deflection (mm)
a=1.0m h=25mm
a=1.0m h=50mm
a=1.0m h=75mm
a=1.0m h=100mm
a=1.0m h=150mm
a=1.0m h=200mm
a=1.5m h=25mm
a=1.5m h=50mm
a=1.5m h=75mm
a=1.5m h=100mm
a=1.5m h=150mm
a=1.5m h=200mm
Square tendon spacing (a)Thickness (h)
Impala
SD site 2 initial
SD site 2 final
Mponeng
Shotcrete Demand (quasi-static)
-
Shotcrete Demand (Dynamic) Roof Prism (Barret &
McCreath
Sidewall: Kinetic Energy
Roof: Kinetic and potential energy
-
0.01
0.1
1
10
100
0.5 1 1.5 2 2.5 3 3.5
Kin
eti
c En
erg
y (k
J)
Span between tendons (m)
0.2 m/s
0.5 m/s
1.0 m/s
1.5 m/s
2.0 m/s
2.5 m/s
3.0 m/sSouth Deep Blast PPV
South Deep Site effect
Mponeng Max PPV
Mponeng threshold PPV
Shotcrete Demand (Dynamic)
-
0.1
1
10
0.5 1 1.5 2 2.5 3 3.5
Po
ten
tial
En
erg
y (k
J)
Span between tendons (m)
Shotcrete Demand (Dynamic)
-
Shotcrete Capacity
Peak/residual strength
Energy Absorption
Standard tests (RDP/ASTMC1550, EFNARC)
Fibre content
Mesh area
-
010
20
30
40
50
60
0 5 10 15 20 25 30 35 40 45
Wp
c(kN
)
Deflection (mm)
Steel 40kg/m3
Steel 55kg/m3
Steel 70kg/m3
Polypropylene 1kg/m3
Polypropylene 2kg/m3
Polypropylene 3kg/m3
Polypropylene 4kg/m3
Polypropylene 5kg/m3
Polypropylene 6kg/m3
Polypropylene 7kg/m3
Polypropylene 8kg/m3
Shotcrete Capacity (RDP)
Peak load
-
Shotcrete Capacity (RDP)
1.E-01
1.E+00
1.E+01
1.E+02
1.E+03
0 10 20 30 40 50 60
mc
(Nm
/m)
RDP Wpc (kN)
25mm
50mm
100mm
150mm
200mm
Thickness (h)
70kg/m3 steel fibre mix40kg/m3 steel fibre mix
55kg/m3 steel fibre mix1-8kg/m3 poly fibre mixes
Impala
South Deep site 2
Mponeng
-
010
20
30
40
50
60
0 5 10 15 20 25 30 35 40 45
Wp
c(kN
)
Deflection (mm)
Steel 40kg/m3
Steel 55kg/m3
Steel 70kg/m3
Polypropylene 1kg/m3
Polypropylene 2kg/m3
Polypropylene 3kg/m3
Polypropylene 4kg/m3
Polypropylene 5kg/m3
Polypropylene 6kg/m3
Polypropylene 7kg/m3
Polypropylene 8kg/m3
Shotcrete Capacity (RDP)
-
Shotcrete Capacity (RDP)
0.00
2.00
4.00
6.00
8.00
10.00
12.00
0.000 0.020 0.040 0.060 0.080 0.100 0.120
mp
c(k
Nm
/m)
(radians)
Steel 40kg/m3
Steel 55kg/m3
Steel 70kg/m3
Polypropylene 1kg/m3
Polypropylene 2kg/m3
Polypropylene 3kg/m3
Polypropylene 4kg/m3
Polypropylene 5kg/m3
Polypropylene 6kg/m3
Polypropylene 7kg/m3
Polypropylene 8kg/m3
Generic
P (Load)
Lever Arm = L/2
-
050
100
150
200
250
300
350
400
0.00 10.00 20.00 30.00 40.00 50.00 60.00
Wc(
kN)
Deflection (mm)
Steel 40kg/m3
Steel 55kg/m3
Steel 70kg/m3
Shotcrete Capacity (on wall)
75mm thick, 1m tendon spacing 8.66 x
1.33 x
-
01000
2000
3000
4000
5000
6000
7000
8000
9000
0.00 10.00 20.00 30.00 40.00 50.00 60.00
EAc(
J)
Deflection (mm)
Steel 40kg/m3
Steel 55kg/m3
Steel 70kg/m3
40 kg/m3 Panel
55 kg/m3 panel
70 kg/m3 panel
Shotcrete Capacity (on wall)
75mm thick, 1m tendon spacing
-
0.1
1
10
100
0 0.2 0.4 0.6 0.8 1 1.2
EAc(k
J)
RDP EApc (kJ)
25mm
50mm
100mm
150mm
200mm
Thickness (h)
70kg/m3 steel fibre mix40kg/m3 steel fibre mix
55kg/m3 steel fibre mix
Impala
South Deep site 2
Mponeng
Shotcrete capacity (Dynamic) RDP
-
Factor of safety
Loading South
Deep Site
2
South
Deep Site
2
Mponeng
116 level
Impala
Deadweight 2.4 2.4 72.1 4.6
Quasi-static 1.0 0.1 9.3 2.6
Dynamic Max 1.1 32.6
Dynamic (3m/s) 0.1 0.9 0.08
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Outstanding work
Large scale panel tests (Kirsten & Labrum)
UDL & point load
Thickness (50mm, 100mm, 150mm)
Mesh & fibre
Large scale panel tests (Shotcrete working group Gerhard Keyter)
-
Acknowledgements
Mine Health and Safety Council (SIM040204)
South Deep Gold Mine, Mponeng Mine, Impala 14#
BASF (Lars Hage), Mash (Hector Snashall)
Geopractica, University of the Witwatersrand
Seismogen (Tony Ward)
James Dube, Hlangabeza Gumede
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