Deposits: miners need to dig deeper

• Shaft sinking can extend the life span of a mine, writes Pedro van Gaalen

Global demand for metals and minerals will experience a six-fold increase by 2050 as the world transitions towards a carbonfree economy, according to the International Energy Agency. As such, mines risk their long-term sustainability if they do not take decisive action today to access additional orebody reserves.

“Due to the cost-efficiencies and shorter time to production, miners typically start with bulk surface mining operations,” says Digby Glover, CEO at United Mining Services (UMS) Group.

In this regard, spiral ramps and declines are popular, but these options only get miners so far. When surface-level reserves run out, miners generally seek other orebodies close to the surface rather than invest in shaft sinking due to the associated costs and lengthy times to completion.

“Miners will often choose to venture into remote areas as shafts are considered a grudge purchase. However, establishing remote operations can prove costly and complex, and if the miner cannot find another reserve, the company risks going bust.”

Glover asserts that sinking a shaft is becoming increasingly necessary and can often make financial sense by extending the life span of a mine by decades. For example, UMS is sinking two shafts at an open pit mine in Botswana. This underground mine expansion project will extend the mine’s operational life span from 2026 to 2040.

“When miners realise they need to look deeper to access embedded orebody deposits, the decision to go underground often comes too late. The process should start as soon as possible as shaft sinking can take up to 10 years to progress from concept to ore extraction.”

Yet miners often shelve capital expenditure on mine expansion projects in response to boom and bust cycles in the mining sector.

“These cycles usually play out over 10-year periods and typically result in a dearth of capital expenditure when commodity prices dip. While the sector recently experienced some reinvestment as the commodities supercycle gathered momentum, mines should always consider going underground independent of market sentiment,” says Glover.

“While there are complex factors at play across various commodities, miners need to start implementing plans to access additional high-grade orebody deposits now to ensure their long-term sustainability.”

Faced with this reality, shaft sinking is gathering momentum globally, with Glover pointing out many projects, including multiple in the notoriously conservative Australian mining sector, as examples.

“We also see opportunities in Europe, North and South America and Africa,” he adds.

In certain circumstances, the sector is seeing a shift in the technology used in vertical boring, with various machines developed that can bore down directly to the orebody in suitable ground.

Anglo American is sinking production and service shafts at its Woodsmith polyhalite project in the UK, using Herrenknecht’s Shaft Boring Roadheader technology to reach depths of about 1,600m.

Applying technology to traditional shaft sinking methodologies also helps to significantly improve safety for mine workers.

“The huge advances realised in terms of safety relate to how we sequence activities, and the ability to remove people from dangerous situations through remote operating capabilities, modern equipment and machine automation,”

For example, in the past, equipment such as the cactus grab proved dangerous when operated by people. Now, miners use remotely-operated grabbers to scoop material, but no workers are allowed on the shaft floor during the mucking cycle, which improves safety and productivity. Similarly, miners can also operate mechanised drilling remotely, thereby minimising the need for workers in the shaft bottom during the drilling cycle.

“These technological advancements have drastically improved safety and productivity on conventional shaft sinking projects over the past 10 years, which remain the leading considerations on all projects,” says Glover.