T took one year of planning for lifting specialist Mammoet to complete the TBM moves in downtown Toronto in just two nights in April 2015.
For the Eglinton Crosstown LRT project, the 10km alignment did not include tunnelling under the existing subway at Allen Road. Instead, in the early morning hours, crews lifted and shifted two 400t TBMs using strand jacks and a gantry system. Each TBM had a 5.74m diameter and measured 81m long.
In a conventional lift of this sort the launch shaft accommodates vertical support columns for the gantry,” explains Mammoet. However, to minimize disruption to the expressway above, the shaft configuration was smaller than usual and did not provide enough space for these columns.
Without the vertical supports, piles in the shaft’s wall were used to provide stability to one side of the gantry. For the other side, a beam was needed that could span the shaft. Mammoet provided an existing beam to cover the span and provide sufficient load bearing capacity without additional reinforcement. With the gantry in place, the first TBM was lifted from the shaft and onto its trailer for above-ground transportation of 100m along Eglinton Avenue.
Once over the subway line, it was lowered down the second shaft using a second gantry and strand jacks onto skid track. The same process was repeated on the following night.
Just as no two tunnelling projects are the same transportation, deliveries and lifting vary on every project. The biggest challenge and the biggest key to success is logistics, says Jeff Wilhelm, director of operations for Mammoet Canada Eastern.
For the Eglinton lifts, like many tunnelling projects, these were sites without storage options in an urban center. “We had to have two basic set ups,” Wilhelm explains, “one at the out put shaft and one at the in put shaft to work concurrently. There were definitely constraints as far as space and logistics.”
Some months beforehand the team at Mammoet walked down its carriers that would be used to haul in their equipment to check out all of the staging locations. The equipment Mammoet used for the lifts was fairly straightforward from engineering scope, he says.
“Our logistics plan was probably the most important thing we did to make sure that we were meeting our schedule and the client’s schedule and getting our equipment where it need to be on time.”
LONDON LOGISTICS
T&T’s Paola De Pascali visited Ben Green, delivery manager for the west section of the Thames Tideway Tunnel and Ivor Thomas, tunnel manager for the Bam Nuttall, Morgan Sindall and Balfour Beatty joint venture, which is coming to terms with the challenges of working on London’s River Thames “This is the smallest site I have ever worked on for this type of operation,” says Thomas, referring to the challenges of working at the ‘cosy’ Carnwath road site on London, England’s, Thames Tideway tunnel, a sewer project designed to catch overflows that would otherwise be bound for the river.
Situated in west London, the Carnwath road site is 250m long, 86m wide at the eastern end and 48m wide at the western end. It is the launch site for the TBM that will excavate the western section of the new sewer.
This site is split into two parts; a main site, and an area of the River Thames foreshore.
SITE SETUP
BMB is constructing the west section, which covers the work taking place from Acton in west London to Wandsworth in southwest London.
“We had to sink a 24m shaft and to build an acoustic shed 18m by 30m and to reconstruct a river wall and to sink 560 piles,” Thomas says. “The whole process required careful choreography on site.”
The site at Carnwath road required the sinking of more than 160 piles, some permanent while others are just for temporary works. “For example it was necessary to reinforce 250m of the river wall to allow the construction of the acoustic shed,” says Thomas. While there is no combined sewer overflow being intercepted at this site, it will be used to drive and receive the main tunnel and a connection tunnel.
RIVER VALUE
An 8m-diameter Herrenknecht EPBM was chosen for the drives in this section, roughly 7km long. The TBM was shipped before Christmas 2017 and the client was eager to bring its components in by water from Germany straight to Carnwath Road. It was then assembled at the surface on site ready for lowering into the shaft. Thomas explains that they weren’t sure of that because it was the first time in London that a TBM was shipped to site entirely by water.
“My personal commitment to road safety comes from witnessing the death of a cyclist at Chelsea Bridge, who was crushed beneath a muck lorry,” says Thomas. “Anyone witnessing a similar accident would try to reduce the number of lorries working in London.
“The 700t shield successfully arrived on site. That was a fantastic piece of hard work carried out by our team. The machine was built inland, some 20km from the River Rhine; it was then transported by road to Kehl to the river, and then transported up the Rhine by barge. It took approximately three days to get to Rotterdam, where it was stored in a yard, and then the components were transferred to a barge to cross the Channel. The barge travelled from Denham Wharf to Gravesend where it stayed for three days to wait for the right weather and tide to bring it up to Carnwath road.
“The whole operation took seven days. The last leg of the journey saw the two tugs procured by the joint venture bring the TBM up the River Thames. These tugs are specially designed to work in this type of environment. The two tugs had an interesting design feature: bridges that could be hydraulically elevated so that the skipper was able to see over the load to the water in front to the barge.”
Thomas adds that the entirety of muck removed is being transported by water. “BMB invested with their site supply chain (AC Bennett) not just in tug boats but also in a new fleet of barges specifically designed to operate in conjunction with those units, which push rather pull,” Thomas says.
“Historically, barges placed on the Thames for waste operations had to be pulled on ropes, whereas the ‘tugs’ were designed to push, so it’s more efficient in terms of safe operation,” Green says. Green adds that not only is the muck going up river by barge, but tunnel segments are being transported to site by barge by water from the Ridham factory.
Thomas adds that another issue for the project was the selection of craneage. “As we are operating in a port, we wanted to find the best solution for off-loading segments,” he says. “We would usually use a crawler crane, but not in this case.
“We visited the port of Cork in Ireland, which has a similar riverfront to the one at Carnwath road and deals with a similar amount of material. We consulted with them to adopt the best logistical solution. They suggested an electrically operated port crane and we decided to go with a Liebherr port crane.”
Green explains it was another investment designed to increase the facility of the river as an asset. “The port crane ensures good visibility for the operator down to the barge, allowing us to reduce the number of people on the barge and the amount of handling required on it.”
WEIGHTED CONCERNS
The sheer weight and bulk of steel rope can be an issue on some lifting jobs. Using a synthetic alternative often makes sense.
As part of its USD 3bn Project clean Lake program, the Northeast Ohio Regional Sewer District (NEORSD) is building more than 20 miles (32km) of sewer in Cleveland, Ohio. The tunnels will reduce CSOs to Lake Erie and its adjoining waterways. For the 4.5km-long Dugway Storage Tunnel contractor The Lane Construction Corporation chose a 27ft (8.2m) diameter Herrenknecht TBM. To complete the critical lifting and lowering of the machine’s components into place Ohio-based PSC Crane & Rigging worked with Courtland, a designer and manufacturer of engineered synthetic ropes, heavy lift slings, electro-opticalmechanical cables, and umbilicals.
PSC provided onsite loading and transport of 12 TBM components from the staging laydown yard to the installation shaft location, and then lowered six of the 12 main components into final position for assembly—the heaviest weighing in at 450t. The lifting specialist explains they off loaded components from Self-Propelled Modular Transporter units with the use of a 700t Hydraulic J&R Gantry System serving as a lift tower, in conjunction with an 800 metric ton Enerpac Strand-Jack system atop 80ft (24m) girder beams spanning a 50ft (15.2m) diameter by 200ft (61m) deep shaft.
Brooks Nunley, technical sales and key account manager at Cortland, explains, “Typically there are two options available to complete these types of projects: wire rope slings or large round slings. Our alternative is the Plasma 12×12 braided rope sling, which is seven times lighter than the weight of a wire rope and about half the size of a round sling. It also only requires about half of the hardware width of most high performance round slings available on the market today.”
As the TBM components were lowered into position for assembly, PSC jacked and slid the TBM assembly components laterally into the starter tunnel approximately 300ft utilizing a 1,000t Hydraulic Hydra-Slide Up & Go skidding system.
Four-inch diameter Plasma 12×12 rope slings were spliced to specifications at 63ft in length, fitted around the TBM and then hoisted by a heavy track hydraulic skidding system with jacking load shoes into the Dugway Storage Tunnel.
The total assembled weight of the TBM that had to be jacked and slided 300ft (91m) into the base of the starter tunnel was 609 metric ton.
Nunley says there are benefits to using lightweight 12×12 rope slings for logistics, job-site storage and safety during projects like the Dugway TBM assembly. “The teams on-site can handle the ropes with greater ease than steel or bulky round sling alternatives.”
TBM excavation started in July 2017 and made its final breakthrough in March. The Dugway Storage Tunnel is set to go into service in 2019, and is the second of seven tunnels commissioned by NEORSD.
