SHAFT SINKING
Watching Woodsmith
The next challenge for Herrenknecht ’ s SBR technology is fast approaching at the Woodsmith project , a polyhalite development owned by Anglo American situated on the North Yorkshire coast of England .
The use of SBRs was slated for this project by Sirius Minerals ( the former owner ) all the way back in 2018 , with orders for two units able to sink production and service shafts with 6.75-m diameters to depths of 1,594 m and 1,565 , respectively . The orders came to Herrenknecht less than a year after Redpath Deilmann secured two SBR machines for its work sinking the 8-m diameter shafts in Belarus .
DMC Mining was initially attached to the sinking of these two shafts , plus two circa-390-m-deep smaller shafts associated with the materials transport system , but Anglo American cancelled this contract around a year ago . A spokesperson , at the time , said the new structure that came with DMC ’ s exit provided the company with simpler internal processes , allowing it to “ better manage the important transition between the sinking phase and ramp-up to steady state operations ”.
During the company ’ s recent investor call , Anglo American Chief Executive , Mark Cutifani , confirmed the small intermediate shaft for tunnel ventilation and access , being developed by blind drilling , had reached its full depth of 383 m at the end of June and was being lined before connecting it to the material transport tunnel to run from Teesside to the mine in Whitby .
Work on the service shaft with the SBR had begun , with the “ first cut ” occurring in late July , he added .
Anglo is in the process of carrying out a review of the sinking project to support compliance with its internal standards . This includes engineering , cost and schedule , with the SBR shaft sinking schedule another element under scrutiny .
An Anglo American spokesperson told IM last month : “ We are now in readiness to commence shaft sinking operations during the course of August , and intend to assess the performance of the SBR over the coming months so we can better predict its forward progress to inform the overall schedule .”
The spokesperson added : “ Regarding the SBRs themselves , several improvements and upgrades have been made to it from the first and
Two Herrenknecht Shaft Boring Roadheaders will be used to sink production and service shafts with 6.75-m diameters to depths of 1,594 m and 1,565 , respectively , at the Woodsmith potash project
second models used at Jansen in Canada and Nezhinsky in Berlarus .”
This includes the addition of two retractable robotic probes to test and grout the ground ahead to facilitate safer excavation , plus the installation of an additional control cabin on surface to reduce downtime by allowing the machine to continue to be operated remotely during shift changeovers . form a station within visual range of the conveyance ; n A full shaft stop control button on every deck of movable work platforms for complex shaft remediation where multiple hoist and rehabilitation platforms may be operating in the same shaft ; n Laser scanners at the collar and sub-collar doors to ensure that collar doors are clear of obstructions and objects that could fall into the shaft prior to opening / closing ; n A “ unique ” under-slung hydraulic excavating shaft mucker to provide the flexibility to cut , chip , or drill and blast the frozen ground ; and n A battery-powered mechanised raise climber , as well as a remote camera inspection unit for similar climber systems , for face inspection prior to re-entry .
Melong said the Redpath group is tendering for several shafts – both sinking and rehabilitation – in Canada , while there are active tenders in Europe and on-going discussions for shaft work in North America as well as Central America .
In the Americas markets , the mechanised sinking technology most frequently discussed is large-diameter raiseboring .
Redpath has had serial success with this technology , and Melong says the option of raiseboring a shaft is more readily being considered in some markets , even if the tradeoffs associated with using this technique are not .
“ Boring shafts for ventilation , versus production or conveyance operation , are two different challenges ,” Melong explained .
“ The investigation into a raisebored shaft versus other approaches such as blind sink can be significant , with aspects such as boreability , stand time , hydrogeology , geo-mechanical and verticality constraints for its end use needing to be clearly understood .”
Often , the volume of waste material the mine must handle among its normal requirements renders the approach unfeasible , inhibiting the mine from hitting its productivity goals as well as well as the mine development targets , according to Melong .
He provided an example of the factors that need to be considered during such investigations .
“ We have recently competed a deep multi-leg raisebore production shaft in Zambia ( Mindola Deeps ) as well as a number of deep holes in that
110 International Mining | SEPTEMBER 2021