Better blasting techniques to protect underground mining infrastructure

Successful and safe mining operations depend on two critical yet conflicting components: supportive structural works that stabilise often dangerous underground environments, and drilling and blasting activities meant to disrupt the rock mass.

Protecting vital infrastructure against damage from blasting operations is a key consideration for a number of functions within mining, from geotechnical engineers, surveyors, and mine planners, to drill and blast teams, operational supervisors, and safety officers. Getting consensus on the best practices to implement can be difficult, which is why mining companies across Africa are reaching out to Mining and Energy Acuity (MEA) for additional guidance and support.

Here are five key blasting and infrastructure recommendations we make to mining companies looking to undertake new operations or simply improve the worksites where they currently operate:

1.     Ground vibration control and monitoring

Limit blast-induced ground vibrations to protect underground structures by establishing site-specific peak particle velocity (PPV) limits for sensitive excavations, and preparing blasts to remain below those thresholds​.

By adjusting blast designs to have shorter rounds, using carefully controlled explosive quantities, and refining blast timing, teams can fire only the necessary charges and reduce peak velocities from the triple-digit mm/s to the low tens. This helps to limit the risk of damage to the surrounding area.

2.     Precision timing and advanced blast sequencing

Utilise modern initiation systems and expertly engineered blast sequences to minimise collateral damage. Electronic detonators with programmable precise delays are considered best practice, because they allow for exact control of timing and firing sequences.

By eliminating timing inaccuracies inherent in pyrotechnic detonators, the explosive energy release can be optimised to reduce vibration and shock to the surrounding rock and, thus, the relevant supporting infrastructure.

Optimising the delay between adjacent holes and rows ensures that charges initiate in a sequence that directs the most energy into rock breaking and away from critical supports, rather than concurrently shaking the whole rock mass.

3.     Preconditioning blasting

Implement preconditioning blasts in deep or highly stressed rock to reduce the risk of rock bursts and infrastructure damage. This involves detonating explosives in boreholes ahead of the advancing face or around a stope or pillar to deliberately crack and weaken the rock mass before the main excavation reaches it.

By creating a fractured “buffer” zone, the high stresses are partially alleviated as the broken rock cannot carry as much load​. This means when the next round is blasted or the face is mined through, the likelihood of a sudden, violent energy release is significantly reduced.

4.     Overbreak minimisation

Keep excavation contours tight by preventing the excessive breakage of rock beyond the designed perimeter. Overbreak – rock broken outside the intended profile – can undermine roof and wall stability, and weaken support installations.

Adopting cautious perimeter blasting techniques, such as presplitting, is essential for achieving clean rounds and minimising overbreak​. This technique can also deliver a near-design tunnel shape while maintaining the integrity of surrounding rock​.

If done correctly, overbreak minimisation can improve rock conditions and support effectiveness, reduce rehabilitation requirements, protect installed ground support, and lower costs.

5.     Ground support designed for blast dynamics

Ensure that underground support systems can withstand the dynamic loads and stress changes induced by blasting. Ground support, including rock bolts, cable bolts, meshes, shotcrete liners, and steel sets, should be chosen and installed with the understanding that blast vibrations and stress waves will pass through the rock.

Rigid or brittle supports may fail or even worsen rockfalls under repetitive vibration, and unsecured bolts can loosen surrounding rock. When exposed to repeated blast vibrations, they can shift, rattle, or transmit energy into the surrounding rock, unintentionally dislodging it, and potentially causing collapses or rockfalls.

Best practice is to use high-capacity, energy-absorbing support where needed. For example, companies can emphasise fully grouted rebar or yielding rock bolts that won’t work loose, fibre-reinforced shotcrete that resists spalling, and cable lacing in larger spans. Well-engineered support works in tandem with blast design, as careful explosive selection and charge distribution can improve the rock mass condition and maximise the capacity of support units​.

Ultimately, however, continually upholding and improving blasting and support standards to protect people and surrounding structures can be complex, and includes a far wider variety of considerations than just the above.

Mining companies seeking to ensure the stability of their operations during blast operations typically consult with expert blast engineering and explosives management service providers such as MEA. The alternative – doing it alone – can be prohibitively expensive for most companies, and will require additional, experienced in-house teams to plan and implement effectively.