Smooth Solutions for Every Mine Manager: Reliable Pre-Driven Recovery Roadways
Longwall operations implement PDRRs to realise safety and productivity benefits
PDRRs involve:
Development of an additional roadway (single or double pass) at the LW take-off
Installation of secondary support and pressure-rated shutters along the roadway and affected intersections
Fully backfilling the PDRR with a specifically designed low-strength cementitious grout delivered via borehole/s.
LW shearing into the grout-filled PDRR at close to full production rates and is recovered from within the supported roadway.
The advantages of a PDRR are:
Reduce personnel exposure to bolting unsupported ground
Faster LW critical approach
Quicker recovery time
Achieve PIC at an accelerated rate
Increases production up to 10-20 days
Advantages & mitigation strategies for weak roof & floor recoveries
For more information, see the 2016 paper “The Evolution of Pre-driven Recovery Roadways at Crinum Mine”.
Over 100 full or partial pre-driven recovery roads have been used in the US, Australian and South African underground coal mines (Thomas, 2008). In every case of recorded failure, standing supports were utilised. There are no recordings of a failed fully grout-filled PDRR.
Our past Pre-Driven Recovery Roadways Jobs
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Grosvenor, Anglo American
Pre-driven recovery roadway PDRR LW104 and 105. Both PDRR’s filled within 28 days on day shift only. This project includes design and construction of a purpose-built plant ready for 2021 project execution.
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Appin, BHP
Pre-driven Recovery roadways PDRR LW705 and LW706 were made by removing a hard stone dyke and refilling with fly ash grout in 2013. Tim Gilroy was Project and Site Manager enabling the development and delivery of two 6000t campaigns with fly ash grout. This project used a single 300m deep borehole and underground reticulation system designed by Tim Gilroy.
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Crinum, BHP
Pre-driven Recovery roadways PDRR LW21, 22, 23 and 24 from 2012 to 2015. Project and Site Manager enabling the development and delivery of four 6000t campaigns with fly ash grout. Tim managed combined drill and fill with 10 off 4” boreholes per PDRR. A total of 18000m3 of grout was supplied. Crinum had previously attempted a partially filled PDRR LW20 and this had failed and decided to continue with fully filled PDRR’s. This project managed to achieve 500tpd utilising 8 powder tanker trucks. All PDRR cuttings were successful with complete roadway filling tight to the roof. Varying strengths were trialled at each campaign to optimise the grout strength.
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Broadmeadow, BHP
Southern Mains were previously mined roadways but then mine plans were changed needing them to be refilled with 36,000m3 grout to enable mining a longwall panel and filling PDRR LW8 and LW9 with 6000m3 each. Tim was Project and Site Manager enabling the development and delivery utilising a system of borehole and reticulation. Tim’s careful filling strategy ensured 100% roof contact by the grout to carry the ground pressure wave from the longwall.
