1. Optimisation of LW Installation Road Support Plans
INIT
Optimisation of LW Installation Road Support Plans
25 February 2010

2. Agenda Background How it was What we did The outcome Conclusion
Questions

3. BACKGROUND New management & Tec Services team at CDCM
Understanding that we would have more install faces that previously planned
LW1B face road had just been completed – with what was considered by many to be excessive support installed.
Question asked as to why?
What was the justification
What was the Geotechnical engineering science behind the support strategy?
A review was undertaken 3

4. How it was
Size of the LW shields etc require a 9 metre wide install face with 10 metre wide at MG & TG and 11m at shearer stable – it’s a big hole.
Original design report
Identified significant lack of geotechnical data in the region of the LW1b Face Road
and used empirical relationships and experience to develop a support plan
The result being a run of face support density of:
10 x 1.8 m roof bolts per metre
4 x 10 m long point anchored tendons per metre
Gate end support density of :
11 x 1.8 m roof bolts per metre
6 x 10 m long point anchored tendons per metre 4

5. For every install face - Remember we have 4 face roads in 1 year
How it was
That’s 1250 tendons.
For every install face -
Remember we have 4 face roads in 1 year 5

6. What we did
Decision was made to undertake a geotechnical design using Numerical modelling to optimise and validate the support density needed.
Agreement that a conservative approach must be maintained
Agreement that CDCM would fill gaps in the data set to minimise the assumptions
Additional data used to update the site sonic/UCS model
A cored drill hole was drilled,
logged
and routine geomechnical testing undertaken.
Acustic scanner run
Bedding strength was still the BIG UNKNOWN 6

7. What we did 7

8. What we did 8

9. What we did 9

10. What we did 10

11. What we did
High Strength Bedding Model – very little deformation, only light cable pattern needed 11

12. What we did
Low Strength Bedding Model – more likely to be the case based on structures seen in roof strata from scanner and cores, moderate density cable pattern needed 12

13. What we did 13

14. The outcome
Size of the LW shields etc require a 9 metre wide install face with 10 metre wide at MG & TG and 11m at shearer stable – it’s still a big hole.
Refined design report
Filled in the Gaps identified in original data set
Built a re-fined Geotechnical model for the strata
Used Numerical techniques, calibrated by actual site deformation data
The result being a run of face & MG end support density of:
10 x 1.8 m roof bolts per metre
3 x 8 m long grouted tendons every 2 metres
TG end support density of :
11 x 1.8 m roof bolts per metre
4 x 8 m long grouted tendons every 2 metres 14

15. Conclusion
That’s 470 tendons. (saving us 800 tendons and a lot of time)
For every install face
Cost of drill holes, testing, modeling <$60k
Saving to the mine per install face >$330,000 per face road
x 4 roads = $1.3 million
Time saving for the development of face roads & confidence in the support strategy used & having a happy mine manager
- Priceless 15