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Proposed Design Methodology for 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 ... – PowerPoint PPT presentation

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Title: Proposed Design Methodology for shotcrete


1
Proposed Design Methodology for shotcrete
  • W.C Joughin, G.C. Howell, A.R. Leach J. Thompson

2
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

3
Design Process
  • Determination of Shotcrete Requirements
  • Excavation requirements
  • Shotcrete function/purpose
  • Is it required?
  • Determination of rock mass and loading
    conditions
  • Rock mass classification
  • Stress modelling
  • 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
4
Rock mass conditions
  • Q/GSI
  • Stress modelling

5
Shotcrete requirements(Excavation requirements)
  • Importance of excavation (access/production)
  • Exposure of personnel
  • Life of excavation
  • Functional dimensions of excavation
  • Maintenance and rehabilitation (redundancy)

6
Shotcrete requirements(Shotcrete
function/purpose)
  • Structural support (Not covered)
  • Fabric between tendons to contain
    jointed/fractured rock
  • To prevent spalling/strainbursting near face

7
Shotcrete requirements(is it required?)
  • Observations of block size and stress damage
  • Keyblock analysis (eg Jblock) (joint controlled)
  • Stress damage (RCFgt0.7, ?1/?c ratio)
  • Empirical charts (joint controlled SRF)

8
Shotcrete requirements
9
Shotcrete requirements
10
Shotcrete Demand
  • Deadweight
  • Quasi-static
  • Dynamic

11
Shotcrete Demand (deadweight)
  • Roof prism (Barret McCreath)
  • Sidewall prism slides
  • Conservative estimate

12
Shotcrete Demand (Deadweight)
13
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.

14
Shotcrete Demand (quasi-static)(Displacement)
  • Displacement monitoring (extensometers)
  • Maximum displacement from Udec GRC modelling

15
Displacement from modelling
16
Shotcrete Demand (quasi-static)(Displacement)
17
Shotcrete Demand (quasi-static)
18
Shotcrete Demand (Dynamic)
  • Roof Prism (Barret McCreath
  • Sidewall Kinetic Energy
  • Roof Kinetic and potential energy

19
Shotcrete Demand (Dynamic)
20
Shotcrete Demand (Dynamic)
21
Shotcrete Capacity
  • Peak/residual strength
  • Energy Absorption
  • Standard tests (RDP/ASTMC1550, EFNARC)
  • Fibre content
  • Mesh area

22
Shotcrete Capacity (RDP)
Peak load
23
Shotcrete Capacity (RDP)
24
Shotcrete Capacity (RDP)
25
Shotcrete Capacity (RDP)
Generic
26
Shotcrete Capacity (on wall)
75mm thick, 1m tendon spacing
8.66 x
1.33 x
27
Shotcrete Capacity (on wall)
75mm thick, 1m tendon spacing
28
Shotcrete capacity (Dynamic)
RDP
29
Factor of safety
30
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)

31
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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