CONTINUOUS CUTTING
TBM world record
Anglo American recently set a World Record for the longest tunnel developed by a single TBM in a soft-rock environment . The record – previously set at 25.8 km – was surpassed by the Woodsmith project team in the UK in late October , when the owner , Anglo American , declared it had reached the 25.9-km mark . This development is part of a 37-km-long mineral transport tunnel to service its 5 Mt / y polyhalite mine .
The machine used at Woodsmith is a Herrenknecht hard-rock TBM that , Tom McCulley , CEO of Anglo American ’ s Crop Nutrients division , says works in a similar fashion to the Herrenknecht Shaft Boring Roadheaders being used at Woodsmith for shaft sinking operations in that it cuts the soils , without blasting , and the material is transported through the machine and out of the tunnel via a conveyor that is part of the TBM .
“ In addition to excavating the material , the TBM also simultaneously lines the tunnel via precast concrete segments ( six segments make up a ring around the circumference of the tunnel ); these concrete segments are fabricated at the Teesside port by a project dedicated facility ,” McCulley said during a recent analyst and investor visit .
He said in every measure the tunnelling on the project to date has been an amazing success , aided by a solid team performance . This team is made up of contractors from STRABAG , Herrenknecht and Anglo American . Progress has been aided by
The Woodsmith tunnel boring team is made up of consistent ground conditions across the contractors from STRABAG , Herrenknecht and Anglo
tunnel within Mudstone strata , McCulley American said .
“ These conditions are very predictable , and cutting is easy for the machine which minimises the bearing wear , which is a key risk area for the TBM ,” he said . “ This consistent strata has allowed us to switch our strategy from three TBMs to one TBM for the entire 37 km , which means we will not only pass the World Record , but we will also smash it when we reach Woodsmith in late 2026 .
“ This reduction in TBMs had a knock-on impact of saving significant capital over what was originally planned .”
Anglo is consistently seeing average rates increase to over 20 m / d and trending closer to 25 m / d , which compares favourably with about 16-17 m / d in late 2021 , it noted .
having the ability to navigate around corners and construct 5.5-m diameter decline access tunnels . The MTB is made up of four track-mounted units containing various parts – the cutter head and bolting section is up front , followed by the transformer and 300 m capacity water and electrical reels on the third unit , and a 14 cu . m capacity storage bunker and discharge system on the fourth unit .
The units are also equipped with conveyors that transport the mucked material along the machine .
Having initially been tested in a quarry in Italy in soft rock in 2018 , the MTB made the trip back to South Africa to start work on a 1.4-km project at Northam Platinum ’ s Eland platinum group metals operation , in harder rock . This project was terminated in March 2020 due to the COVID-19 pandemic .
The MTB was then deployed on the Sandsloot Exploration Decline at Anglo American Platinum ’ s Mogalakwena PGM mine , in South Africa , as part
of a turnkey contract with the mining company . This work was ultimately cut short , with Koos
Jordaan , Master Drilling Director telling IM that the company was working through all the learnings with a “ rebuilt and reworked ” MTB likely to be ready for deployments in 2024 .
“ The elements that are holding back the MTB are not necessarily tied to the machine itself ; it is everything that needs to be done with it ,” he said . “ As a contractor , we are looking at working simplicity , reliability and how the whole system works so we can execute the job efficiently and safely .
“ One of the major learnings we had was the need to concurrently carry the services and engineering with you on a decline . With the next iteration , we are expecting better and more consistent performance than we had at Mogalakwena .”
A second-generation MTB is also in the works in partnership with a mining company . This is likely to cater to 6.5-m diameter tunnels and be ideally matched to establishing twin declines .
A square cutter concept for flat roof , side walls and floor – instead of the circular excavations offered by the existing MTB – is also in the Master Drilling innovation pipeline , as are developments around “ cut & break ” technology and reef mining .
Outside of collaborations with mining companies , Master Drilling is opening up to the equipment makers themselves in this sector , with personnel having visited several test sites over the last 12 months to scope out potential partnerships and projects .
“ We have significant experience as both technology maker and contractors ,” Jordaan said . “ You only have to look at our record in the raiseboring space to realise how effectively , efficiently and safely we can cut hard rock over significant distances .
“ We believe we have something unique to offer the sector .”
The MTB is designed to work on both inclines and declines , with the first generation machine having the ability to navigate around corners and construct 5.5 m diameter decline access tunnels
IM
International Mining | NOVEMBER / DECEMBER 2023