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Proposed Design Methodology for 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.

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Proposed Design Methodology for shotcrete

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  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 (RCF>0.7, 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) • Sidewall: Kinetic Energy • Roof: Kinetic and potential energy • Roof Prism (Barret & McCreath

  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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