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Optimisation of LW Installation Road Support Plans

This case study discusses the background, process, and outcome of optimising the support density for LW installation road, resulting in significant cost and time savings.

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Optimisation of LW Installation Road Support Plans

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  1. 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. 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

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