Underground experiments for enhanced health and safety

Machines are many but workers few. Much has been mechanised since the last expansion of the metro. But one thing is the same. The heavy work of pushing in several metre-long bolts to secure the tunnel roof is still done manually. However, deep under Södermalm, experiments are under way to mechanise this procedure.

News News 2023-03-28

Kalle Pellinen gillar den

Inside a warm, cosy cabin sits the bolt rig operator Kalle Pellinen. It takes him four minutes to drill a hole, fill it with cement and then insert the bolt. The only thing that can be heard is Kalle’s Spotify list.

“I have inserted bolts manually as well. It is heavy, hard on your back and shoulders and the cement splashes. This machine entails a significant difference, I can only see advantages,” says Kalle Pellinen.

So far, however, there is one experiment which is in progress just over 100 meters under Sofia church in Södermalm, the third consecutive experiment. This series of experiments is a collaboration between the Region Stockholm, the contractors constructing the tunnels and the companies manufacturing the machines.

New way of thinking

“We have learned a lot. It’s not just about bringing in a machine and starting to bolt, rather this entails a new way of thinking and planning,” says Martin Hellgren, Manager in charge of the expansion from Kungsträdgården to Nacka and to Söderort.

Bolting has been mechanised since long in the mining industry but the demands there are different.

“Our bolts should last at least 120 years. Within mining, the period is much shorter. We must make sure that the method is efficient as well as suitable for various types of rocks. Also, the bolts should last their entire life span,” says Martin Hellgren.

Significant difference for the industry

So far the results of the experiments look good. The three experiments will be fully evaluated by the end of the year.

“We want to be involved and lead the technological development in mechanised bolting. If we succeed, it can make a great difference to the industry,” concludes Martin Hellgren.

Experiment 2, in the tunnels under the Hammarby Canal, is a finalist in an annual health and safety competition for the construction industry. The competition will be concluded at lunchtime on Tuesday, March 28.