metodologia del shotcrete

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 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


(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 (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)


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)


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








Shotcrete Capacity (RDP)

Peak load


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











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









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

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

metodologia del shotcrete

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