Safety guidance and training for tunnellers can boost efficiency and reduce costs.
ANDt has been a busy time for tunneling projects. Tunneling work on London’s 25km Tideway super sewer officially finished in April. The two tunning boring machines (TBMs) working on High Speed 2’s (HS2’s) tunnels under the Chilterns completed the first stage up to the ventilation shaft at Chalfont St Peter in March. And work continues apace on the Silvertown Tunnel in east London.
But before projects reach major milestones there are challenges to be overcome and accidents can occur.
Need for harmonized training
When it comes to health and safety, client organizations have their own training requirements and, as it stands, these are not aligned to those of other projects. As such, contractors – and particularly labor subcontractors – have to spend money on a plethora of courses.
This is where the Transforming Tunneling Safety (TTS) Group comes in. Formed in 2014 by client organizations, the group is pushing for industry-approved courses along with an increased openness to help the industry learn from mistakes.
Alongside the British Tunneling Society (BTS) – which promotes the TTS Group’s work – the group is sharing best practice so standards can be raised while the risk of accidents is reduced.
It is hoped that this will transform the health and safety performance on tunnelling work projects in the UK. It could also show cost and efficiency benefits in the process.
When things go wrong on site, people tend to clam up and keep them in house rather than sharing them
HS2 Ltd client director and TTS Group chair Malcolm Codling says that currently the industry is “inherently bad” at sharing lessons learned.
“When things go wrong on site, people tend to clam up and keep them in house rather than sharing them,” he says.
Mott MacDonald program manager Nick Butler, who chairs the TTS Group’s communications working group adds that transparency is key.
“In the past when there’s been an incident it has been kept under wraps for a variety of reasons,” he says. “We’re trying to make it easy for the industry to help the industry out.”
As such, the group has put a bank of information on the BTS website. It shares lessons, good practice guides and safety videos from major projects like Tideway and Crossrail.
Butler explains: “If you’re a busy tunneling engineer and you’re trying to plan railway works, you’ll find issues with locomotive and railway design that you should be taking on board. It’s information provided by the industry for the industry so we can avoid making the same mistakes. ”
Taking the lessons forward
Issues highlighted on the website include three locomotive collisions in Tideway’s main tunnel. One of the incidents occurred during the installation of a 3.3kV transformer approximately 6.5km into the tunnel. Key findings include the observation that having two locomotives on the same track when the crashes occurred was “out of the normal cycles at this stage of the work”.
The lessons learned report produced by Tideway adds that the different teams’ intentions had not been clearly communicated. It adds that the leading car of one of the trains had not been fitted with camera to give visibility to the operator.
An injury occurred on phase one of the London Power Tunnels project when a concrete pump’s hose broke free after it was inserted into shuttering, striking an operative.
It noted a failure to fully identify hazards associated with concrete pumping activities and that appropriate controls had not been recorded before work began.
In addition, it was found that operatives lacked sufficient control of the operation and that the design of the shutter configuration hindered the insertion of the delivery hose to the correct depth for the concrete pour.
The TTS Group hopes that by sharing lessons like these, other projects will avoid the same mistakes.
Good health and safety practice can also reduce costs and increase productivity.
Butler highlights an example on Tideway’s Lee Tunnel, completed in 2016.
There was a lot of flint in the Chalk being excavated and the risk was that if the disc cutters were too small, the flint would damage them. This would make it necessary for operatives to access the cutterhead to change the cutting tools.
“So the team used 482mm double disc cutters instead of 432mm ones. That meant we went in three times in the whole drive instead of about 10, ”Butler says. He explains that this is because the biggest discs were less prone to damage.
“It was good health and safety, and we also didn’t have to stop the tunneling machine as much [for interventions along the tunnel drive]”Butler explainwith.
“So we could get more productivity which means we saved money.”
ANDn tunneling, there are so many different training courses t difficult to find out which ones you need
A more recent example is the 5.6m diameter steel thrust frame or foreshunt from which one of the Tideway TBMs pushed itself forwards at the Greenwich adit. Normally these are removed after tunneling is complete, but in this case it was concreted into place and used to form the permanent works.
Doing so reduced congestion at the base of the adit and created a simpler to operate site with fewer risks and a safer working environment. It also reduced costs associated with the purchase of the foreshunt and time to erect and dismantle.
The result was improved health and safety management and a better commercial outcome.
Balfour Beatty tunneling manager and TTS Group member Roger Bridge says all of this is about “safety by design first ”adding that if this concept is adopted, other benefits will follow.
The TTS Group is consolidating best practice and benchmarking role levels and criteria for occupations involved in shaft and tunnel construction into what it calls the Skills, Knowledge, Attitude, Training and Experience (Skate) matrix.
The idea is to help develop industry-approved courses to provide a good level of knowledge that will be consistently requested by all clients. The BTS website now sets out the skills needed for different jobs.
“It’s making it as easy as possible for people to understand,” Butler explains. “In tunneling, there are so many different training courses that it’s very difficult to find out which courses you need.
“We’re trying to get an absolute baseline and for everyone to agree on courses so whether you work on Tideway or HS2, for example, it works. ”
Bridge adds that the approach should avoid the need for retraining.
“The supply companies were constantly retraining guys which means more cost,” he says. “It needs to be consistent.”
The TTS Group is currently drafting a section of the Skate matrix to fit in the next update of the British Tunneling Society Specification for Tunneling. It is also trying to get the matrix built into the Joint Code of Practice.
The TTS Group is also looking at immersive learning using virtual reality to train workers in a lower risk, off site environment.
Another area for improvement is communication. Bridge has identified a lack of communication between clients as an issue.
Butler adds that regulation is as important as communication.
“If the regulator says you’re going to do that – for example the Environment Agency and Ofwat with Thames Water – you have to do it or you get fined,” he says.
There is also an opportunity to leave a positive legacy for the industry, Bridge says, and Butler adds that they are keen for organizations – contractors and clients – to submit information for sharing no the TTS web page at www.britishtunnelling.com
“It’s a great industry to be in,” he says. “These are massive projects and it’s a privilege to be a part of them. It’s only dangerous if you haven’t planned properly. ”
Codling also emphasizes the importance of involving and engaging people. “It’s about encouraging people to learn from other industry leaders to say ‘we have this issue or innovation that will make your lives easier but also much safer’,” he says.
“Sharing with pride is just as important as sharing with pain and it’s something we need to encourage everyone to do.”
Silvertown Tunnel update
The under construction Silvertown Tunnel is a 1.4km twin bore road tunnel that will connect the Greenwich Peninsula to Newham and the nearby A12 and A13 trunk roads.
The £ 1bn scheme was granted a development consent order in May 2018. It is being constructed via a design, build, finance and maintain contract awarded to the Riverlinx consortium comprising Bam Nuttall, Ferrovial Construction and SK Ecoplant in May 2019.
Tunneling is set to start this summer, with the majority of the tunnel boring machine (TBM) parts now delivered to site for assembly. At 11.91m, the machine which will be the largest diameter TBM
to be used in the UK.
Transport for London head of delivery (Silvertown Tunnel) Helen Wright says: “Cutterhead and tailskin shield welding works are complete and assembly of the conveyor belt to transport spoil to barges is progressing at pace, with all major structural components now installed.”
On the north side of the river in Newham, the TBM launch chamber is close to completion. On the south side in Greenwich piling for the tunnel portal building is complete and pile cropping is underway.
“At the rotation chamber [in Greenwich],
where the TBM will be turned around before tuning the other bore, ground treatment works continue with more than two thirds already installed, ”adds Wright.
Reducing the environmental impact of the project has also been a focus. Cleaner fuel is in use on site and the river is being used for deliveries to keep trucks off local roads. The concrete tunnel rings contain ground granulated blast furnace slag.
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