1. Challenges in mine seismology
Steve Spottiswoode
CSIR

2. Some challenges facing Mine Seismologists
Socio-political environment
Economic and cultural globalisation
Risk-aversion and safety
Who are we? Are we geophysicists or rock
engineers?
Science (rock strength)
Forecasting: long-term
Prediction: short-term
Seismology and engineering
Preconditioning
Managing strong ground motion
How to use numbers from forecasting and prediction?
Near-field vs far-field ground motion
Which events are going to be damaging?
Mining for less rockburst damage & risk
© CSIR

3. Socio-political environment
Are we geophysicists or rock engineers?
Economic and cultural globalisation
Rock Mechanics conferences, especially Australia, South Africa & Canada
Mining companies increasingly source information from around the world.
“Just Google it”
Boom and bust conditions (sourcing post-grad students)
Risk-aversion and safety
Investors want to quantify the risks before committing money
Financial & safety (will not mine under unsafe conditions)
Where, when and how large will the next potentially damaging tremor be?
“Seismologist sometimes needs reminding that there is a real world with problems seeking practical engineering solutions.
Engineers sometimes need reminding that there is a lot to be learned by properly analysing the problem.”
(Wesseloo, 2009)
© CSIR

4. Rock strength Sources at high stress s1
What is the rock strength and how do miners and tunnellers handle failed rock?
At a recent conference (SHIRMS) considerable discussion focussed on describing the strength of rock (e.g. Kaiser).
The most interesting aspect is in the low-stress region close to mining excavations.
Sources at high stress s1
Many modifictions of the Hoek-Brown strength criterion s3
Damage at low stress, often in already damaged rock
© CSIR

5. Can we predict events?
Mining seismicity offers many opportunities (challenges) for quantitative models with long-term drivers such as:
Stress
Stress change or energy “forecasting”
Geological discontinuities
Aftershocks
Can we predict seismic events in the short term?
Summary of the state of the art for earthquake prediction was presented by Tom Jordan yesterday
As with earthquakes, no, but roof collapses and open-pit failures do seem to be predictable
Why?
© CSIR

6. Nature works hard to close up mining voids
What controls the amount of seismicity?
© CSIR

7. Stress and stress change
Seismicity driven by active mining
Seismicity near old mining
© CSIR

8. Mining as a driver of seismicity
© CSIR

9. Drivers of seismicity: geologcal discontinuities
© CSIR

10. Short-term prediction
Tom Jordan referred yesterday to the “heroic quest” of searching for the “silver bullet” or intuitive approach to looking for precursors
Some mines in SA follow a policy of asessing seismicity on a daily basis to provide estimates of seismic hazard.
Hazard changes as mining geometry changes, but does seismicity hold additional information?
From aftershocks? Yes
From changing patterns of seismicity?
Successful predictions of falls of ground?
© CSIR

11. Short-term variations in seismicity by stacking events before & after large events: M>2.5 & 100m in plan
Cumulated seismicity, with adjustments for long-term average
Running average of properties
© CSIR

12. Radar is being used to predict slope stability
Deformation rate
Naismith (2005)
© CSIR

13. Predicting falls of ground in a platinum mine with seismicity
Cumulated seismicity
© CSIR

14. Seismology and engineering
Preconditioning
Managing strong ground motion
How to use numbers from forecasting and prediction?
Near-field vs far-field ground motion
Which events are going to be damaging?
Mining for less rockburst damage & risk
© CSIR

15. Engineering the rock by preconditioning
© CSIR

16. Engineering: Managing strong ground motion
How to use numbers from forecasting and prediction?
Must be ~10 times more likely for prediction
Near-field vs far-field ground motion
Many questions on strong ground motion
Which events are going to be damaging?
Mining for less rockburst damage & risk
Keep people away from possible rockburst damage
© CSIR

17. Conclusions Socio-political environment Science (rock physics)
Defined risk and high safety
Mines see seismologists as working for rock engineers?
Science (rock physics)
Forecasting: long-term
Prediction: short-term
Engineering
Preconditioning
Managing strong ground motion
How to use numbers from forecasting and prediction?
Near-field vs far-field ground motion
Which events are going to be damaging?
Mining for less rockburst damage & risk
© CSIR

18. Thank you Ray Durrheim and Milton Kataka for digital material
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