CONTINUOUS CUTTING three now part of a consortium , led by CMIC , looking at developing a second generation MX650 .
LKAB ’ s tunnelling test
LKAB ’ s strategy , which aims for zero carbondioxide emissions from its processes and products by the year 2045 , has roots in “ mining iron ore profitably and safely at greater depths ”.
It is set to achieve this by incorporating the benefits of digitalisation , automation and electrification in its operations ; building capacity to produce Direct Reduced Iron , and assessing the potential for by-products from iron production , including those derived from rare earth metal oxides and phosphorous .
This strategy has seen the company engage with the mechanised mine development community , looking for solutions that can both accelerate access to its orebodies , as well as improve the safety associated with developing future mining operations .
Part of this plan to mine iron ore at greater depths involves accessing deeper parts of the Malmberget mine in northern Sweden . The company plans to extract a reserve totalling 317 Mt , comprising 306 Mt at 40.4 % Fe magnetite ore and 11 Mt at 46.6 % Fe hematite ore , with extraction planned over a period ending in 2045 .
Technical studies being conducted by LKAB to assess potential for successful , future deep , high-rate mining are working to identify approaches that mitigate risk from stress and seismicity on mining and infrastructure . This includes aspects such as new hoisting alternatives , mine sequencing and production rate , and product mix .
Tristan Jones , LKAB ’ s Strategic Head of Mining Technology , says these studies include a tunnelling test linked predominantly to the mine development method it is expected to choose to access deeper orebodies .
“ That is a risk management effort ,” he told IM . “ We need to understand where we can safely apply mechanical development and where we cannot .
“ For us , the big questions surround how mechanical development is going to work in the host rock , where the stresses are more stable ; and how it is going to work in the production areas , where we have massive mining-induced stresses .
“ The tunnelling test is designed to answer those two questions .”
Jones and his team attempted to bring in either a prototype or commercial mechanical development machine from one of the existing suppliers on the market to conduct this test but have since settled on a different method . “ We are going to take a mechanical development method that has no business building tunnels and we are going to use it to build tunnels ,” he explained .
“ For the size of the test and length of the tunnels , we have deemed it way too much in terms of logistics , cost , time , preparation work , etc to bring in a variation of a TBM , so , instead , we will go simple – we will bring in a big diamond-bladed saw and cut slices of the rock and then use rock breakers to break them out .
“ This process is not about testing the development method – it is about comparing the behaviour of mechanically-excavated tunnels when constructed , and , most importantly , when they are exposed to stress changes . Looking at tunnel damage , induced seismicity and rock reinforcement , now and in the future .”
Work on these tunnels is expected to start next year and carry through to 2026 , with observations and analysis taking place for two years .
“ That timeframe completely depends on the mining development rate and when we induce those stresses ,” Jones clarified .
Master Drilling rocking excavation
Master Drilling is in a somewhat unique position in this space being both a technology provider and a contractor able to deploy said technology .
Its technology remit covers both horizontal and vertical mine development , surface exploration drilling and digitisation , but it has several specific areas of development related to horizontal continuous rock excavation .
The first is its Mobile Tunnel Borer ( MTB ), a TBM-style machine designed to work both on inclines and declines , with the first-generation machine having the ability to navigate around corners and construct 4.5-5.5-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 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 has since been trialled twice in South Africa – both at platinum group metal operations – and a “ Mark 4 ” version of the first-generation machine is now ready to go out in the field .
Some of the main improvements Master Drilling is working on include optimising the production time and minimising downtime through , among other initiatives , upgrading the dewatering capacity for decline development and optimising the dedusting system on board .
Related to this , Master Drilling recently signed a joint development agreement with China-based
China Railway Construction Heavy Industry Corporation Ltd ( CRCHI ), a global leader in tunnel engineering , looking to propel the development of a next-generation tunnel borer . This machine is a bigger system for larger access requirements , with the recent pact including the placement of an order for a powerful 6.5 m-diameter secondgeneration MTB . Negotiations on a tender for this machine are expected to be finalised next year .
Another area to mention here is reef boring , a technology that could pique interest in Master Drilling ’ s home market of Africa .
Having started with a desktop study and progressed to a cutter and penetration test on disc cutters and the chromitite ore and pyroxenite host rock at the Two Rivers platinum mine , Master Drilling has progressed to the point where a cutting and chip removal system has been developed , tested and refined .
The rest of the reef bore system – a joint development with African Rainbow Minerals that , at the front , is made up of four counter rotating cutterheads that produce a rectangular cutting profile – is being assembled and built to be tested in the first half of 2025 in Fochville , South Africa , before underground trials at African Rainbow Minerals ’ Bokoni mine later that year .
Benchmark the boring
While CMIC continues to broker discussions between the mining company , mining contractor and OEM community when it comes to engaging with and advancing mechanised cutting technologies – as well as exploring rock conditioning and pretreatment of the face to potentially boost productivity of mechanical rock excavation – it is also pursuing a way of both quantifying the industry opportunities and assessing the validity of regularly used benchmarks and metrics .
Trevor Kelly , Innovation Manager of Mining at CMIC , explained : “ Mechanised cutting technologies will always get benchmarked against traditional drill and blast practices , so it makes sense that this process is transparent and standardised , using relevant and equivalent inputs that are easily calculated and understood to enable a true comparison of the two . When you can overlay this with the opportunities to deploy the technology – there may be mines with mechanised development opportunities of perhaps multiple kilometres , for example – and you can get a true picture of the financials involved for each excavation method , the two methods may be closer in cost than we think . “ Add this to the well-known safety and environmental benefits associated with the current slate of mechanical cutting machines on offer , and there is a strong case for further adoption of this technology .” IM
NOVEMBER / DECEMBER 2024 | International Mining 59