Title: Proposed Design Methodology for shotcrete
1Proposed Design Methodology for shotcrete
- W.C Joughin, G.C. Howell, A.R. Leach J. Thompson
2Research 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
3Design 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
4Rock mass conditions
5Shotcrete requirements(Excavation requirements)
- Importance of excavation (access/production)
- Exposure of personnel
- Life of excavation
- Functional dimensions of excavation
- Maintenance and rehabilitation (redundancy)
6Shotcrete requirements(Shotcrete
function/purpose)
- Structural support (Not covered)
- Fabric between tendons to contain
jointed/fractured rock - To prevent spalling/strainbursting near face
7Shotcrete 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)
8Shotcrete requirements
9Shotcrete requirements
10Shotcrete Demand
- Deadweight
- Quasi-static
- Dynamic
11Shotcrete Demand (deadweight)
- Roof prism (Barret McCreath)
- Sidewall prism slides
- Conservative estimate
12Shotcrete Demand (Deadweight)
13Shotcrete 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.
14Shotcrete Demand (quasi-static)(Displacement)
- Displacement monitoring (extensometers)
- Maximum displacement from Udec GRC modelling
15Displacement from modelling
16Shotcrete Demand (quasi-static)(Displacement)
17Shotcrete Demand (quasi-static)
18Shotcrete Demand (Dynamic)
- Roof Prism (Barret McCreath
- Sidewall Kinetic Energy
- Roof Kinetic and potential energy
19Shotcrete Demand (Dynamic)
20Shotcrete Demand (Dynamic)
21Shotcrete Capacity
- Peak/residual strength
- Energy Absorption
- Standard tests (RDP/ASTMC1550, EFNARC)
- Fibre content
- Mesh area
22Shotcrete Capacity (RDP)
Peak load
23Shotcrete Capacity (RDP)
24Shotcrete Capacity (RDP)
25Shotcrete Capacity (RDP)
Generic
26Shotcrete Capacity (on wall)
75mm thick, 1m tendon spacing
8.66 x
1.33 x
27Shotcrete Capacity (on wall)
75mm thick, 1m tendon spacing
28Shotcrete capacity (Dynamic)
RDP
29Factor of safety
30Outstanding 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)
31Acknowledgements
- 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