Crossrail is to dramatically cut safety risks and silica dust exposure during operations to drill 250,000 holes in its concrete tunnel linings by deploying a robotic drilling rig.
According to Steve Crofts, head of health and safety improvements at Crossrail, the rig will eliminate Hand Arm Vibration (HAV) risk for workers, and increase accuracy and control. It also uses hollow-tipped drill bits to reduce levels of harmful dust.
The holes are needed to mount overhead power equipment and cabling trays. The rig moves along the tracks and is capable of drilling all the holes in a 200m stretch in a shift. In total, it will cover 21km.
According to Rail Engineer magazine, the system works in conjunction with 3D laser surveys of the tunnel to ensure accuracy.
The ATC joint venture of Alsthom, TSO and Costain, awarded the £300m tunnel fit-out contract in 2012, has developed the rig with manufacturer Rowa Tunnelling Logisitics, based in Switzerland.
"People are now using readily available technology. It allows people to discuss the reality in front of them, not just say ‘there was a problem’."
Steve Crofts, Crossrail
Crofts told Construction Manager that the robotic system was one of series of health and safety innovations, both technological and behavioural, identified via Crossrail’s Gateway Assessment Scheme.
This is designed to promote the raising of standards and sharing of good practice, and incentivise, measure and celebrate health and safety excellence on Crossrail and within the construction industry. “We find innovations on one site, and then we start seeing them trickle across multiple contractors,” says Crofts.
These included “hook-cam”, a camera that streams live images from the hook of a crane to the crane operator or any networked screen, including the site team’s smartphones.
“It can be used to keep a record of all the lifts, so that if there’s an incident they have evidence. Or it can be used to make sure the lifting operations are being improved, and make sure the guys pick up on any briefings,” says Crofts.
Another safety innovation has been trials of secondary cast linings, as an alternative to spray-on concrete tunnel linings. “Fall-out” of spray-applied concrete caused the only fatality to date on Crossrail, when Rene Tkacik was killed in March 2014. The new system involves a moving shutter that clamps on to the tunnel lining.
“Potentially, if it had been available earlier, it would have had benefits. We are looking at the efficiency, cost and speed, which might be slightly slower, but there are obvious health and safety benefits,” says Crofts. “But because we have done spray concrete lining, we’ve moved the industry on in terms of how it’s done and planned. At the start, it was accepted that there would be fall-outs, it was a foregone conclusion. But now they’ve done a lot of work on how you prevent the fall-out from happening.”
The new linings technique has been used at Liverpool Street, Farringdon, Tottenham Court road and Bond Street stations, plus cross passages and shafts.
Other innovations being trialled include wrist-mounted HAV monitors, which more accurately measure individuals’ exposure than tool-mounted monitors. And head-mounted GoPro cameras are being used to film activities for training purposes.
“People are now using readily available technology. It allows people to discuss the reality in front of them, not just say ‘there was a problem’. Or it can be used to review good practice,” says Crofts.
