DRILL AND BLAST | TECHNICAL


Henki Ødegaard, senior engineering geologist


at Multiconsult, tells T&T: “The Rapid Step-Rate Test (RSRT) approach can obtain stress data faster and without hindering the ordinary drill-and-blast excavation cycle much, thus enabling the execution of more measurements than is current practice.” He adds that this ‘more distributed approach’ to


rock stress testing does not demand many new types of equipment to secure the practical and economic benefits of gaining much more real data. Typically, the equipment mainly used on drill-and-blast tunnel projects is needed, adds Ødegaard, whether for new tunnels, or the work in existing tunnels for maintenance or rehabilitation. New equipment continues to be introduced by


industry in support of drill-and-blast, such as Sandvik’s new DT923i jumbo rig and the latest version of the company’s iSURE excavation process control software. Epiroc too has a new boomer, drill and semi-automated explosives charging system. While government policy initiatives and industrial


investments look at ways to help mitigate climate concerns, and new technologies are starting to emerge at mass-scale more economically, such as large electric battery technologies, the switchover to adopting such systems underground is still getting underway, especially in tunnels compared to mines (see box panel 1). Meanwhile, one could be forgiven for thinking it was


all about TBMs but in fact, there are plenty of tunnel projects on the go using drill-and-blast. Fleets of new and owned jumbos are at work globally on multiple large and smaller project challenges, bringing trademark flexibility and adaptability to geological conditions. While TBMs get increasing attention on projects, drill and blast, and other traditional ways of excavation, are being employed to perform cumulatively large sections of major projects; one example is on the Lyon- Turin Base Tunnel currently underway on the Italian- French border (see box panel 2).


ROCK STRESS MEASUREMENT “I believe we have to abandon the idea that rock stress can be predicted a priori,” says Ødegaard, “at least to the level of accuracy required for detailed design purposes of unlined pressure tunnels.” His PhD research, recently completed at the


Norwegian University of Science and Technology’s (NTNU) Research Centre for Hydropower Technology (HydroCen), and supervised by Prof Bjørn Nilsen, looked primarily at in-situ rock-stress measurements at specific areas of tunnels, where the headrace lining changes from high-pressure steel-lined penstock to, just upstream, unlined rock tunnels. With the lining transition zone having to be judged where best to be, its location affects the construction choices, as well as the cost and performance of waterways, and as such the PhD research project was requested by HydroCen industry partners.


1 COMING OF BEVs UNDERGROUND


Waves of new technologies wash through and transform many fast-moving, retail-facing sectors of industry, such as automotive and computers, but older, more traditional, larger mass-to-shift industries, like construction, are often slower to change, usually left in their wake. Change does come, to underground tunnelling too, and among the next wave of advances is adoption of battery electric vehicles (BEVs). But not quite yet. “We have had a lot of questions about BEVs in tunnelling but it’s not really


booming yet like in mining,” Tommi Salo, Sandvik’s product manager of tunnelling drill products tells T&T. “Tunnelling drills have already a ‘hybrid solution’ with electric drilling function and the tramming with diesel engines. Tramming distances are usually short in tunnelling compared to mining and the diesel engine is used only briefly. Salo notes the trend toward BEVs but observes: “It’s changing quite slowly,” and estimates that within 10 years almost all new tunnelling drills will be BEVs. A key factor will be contractors comparing total cost of ownership (TCO) against diesel equipment and then “they will change rapidly to BEVs, I think.” On other aspects of BEVs, Salo says they require less maintenance in mining and tunnelling. “Good points are also that there is electric drilling in underground equipment and electric grids in place. Batteries are easy to charge during drilling and that doesn’t require any extra time.” Further, Salo adds, the same technology developed for mining can be used


for tunnelling. The possibility exists to use its DD422iE BEV development drill for tunnelling applications because the carrier is modular and only the booms would require changing. New BEVs for mining also recently include the TH550B truck and Toro LH514BE loader, and the DS412iE automated rock bolter. Sandvik won one of its highest monthly total orders for mining BEVs last year for seven underground haul trucks and two loaders in Canada. Epiroc recently completed acquisition of a small Canadian business, FVT


Research, specialising in converting mining vehicles from diesel power to battery electric power. FVT designs conversions kits and rebuilds the machines, such as recently converting a Scooptram ST1030 loader. The company also bought electrification infrastructure company Meglab; is


collaborating with ABB on electric trolleys for mines; and has a new version of its battery-electric driven Boomer E2 that is equipped for autonomous operations. By the end of the decade, Epiroc aims to have a full range of emission-free


products overall, but will do so sooner for underground equipment. For those non-electric machines sold the aim is to halve their CO2


emissions by 2030, and similar reductions are wanted for supply chain partners.


Above: Sandvik DD422iE SOURCE: SANDVIK


February 2022 | 39


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