A rubber safety screen falls away from a newly blasted rock at one of the many faces forming an 18-kilometer-long tunnel being built to divert traffic away from Sweden’s capital city. As well as easing pressure on Stockholm’s congested routes, the tunnel—one of the world’s longest— is introducing collaborative 3D engineering to Swedish infrastructure.
With varying degrees of digital expertise, the national highways authority Trafikverket and the designers and contractors on the $3.6-billion E4 bypass project now are embracing building information modeling in a big way, some for the first time. Even official bid documents are digital and in 3D.
“We are the first major project in Trafikverket working on a big scale with BIM,” says Jesper Niland, the owner’s technical manager. At the conceptual stage, project design teams worked conventionally and then moved into 3D modeling, he adds. In the beginning, “there was quite a low understanding of BIM,” he observes.
Even for the contractors, “it was a learning process during the bidding time,” says Maria Christiansson, design manager with locally based NCC Construction A.B. on the northern interchange contract. “Some of us were ready, but not all of us.”
The 21-km-long bypass will arc around the western side of the city, between Kungens Kurva to the south and Häggvik to the north. It will divert traffic from the major E4 north-south highway, which now joins the city’s ring road. Trafikverket, forecasts 140,000 vehicles a day using the bypass by 2035.
Between Kungens Kurva and the E18 highway at the northern Hjulsta interchange, some 16.6 km of continuous rock tunnel will form most of the bypass. From Hjulsta, it will cross various obstacles on a bridge before dropping into the 1.4-km Akalla rock tunnel; from there, it will rise to rejoin the E4 at a new interchange at Häggvik.
The bypass will cross under Lake Mälaren and its Lovön Island, where an underground interchange will connect with surface roads. Farther north, ramps to the surface will serve another interchange at Vinsta. At its deepest, the tunnel will be 60 meters below the surface of Lake Mälaren and almost 100 m below ground level.
Each of the roughly 16-m-wide, 7-m-tall tunnels will have three lanes, increasing to four at the six interchanges along the route. Internal enclosures will shelter the roads form any leaking water. The two tunnels will run about 10 m apart and be linked with security cross passages.
Granite rock along the route “is fairly impermeable, but we have occasional major fault zones,” says Johan Brantmark, Trafikverket’s project director. Contractors are drilling and blasting tunnels, having pre-grouted from the surface where needed. Exposed rock is supported with rock bolts and sprayed concrete. Including 14 km of ramps and nearly 3 km of access drives, the project calls for approximately 50 km of tunneling.
Stockholm’s bypass secured official approval in 2009, leading to the start of procurement. Two years later, Trafikverket awarded a design contract to Grontmij A.B. and Golder Associates A.B. for the big Kungens Kurva interchange.
Bigger contracts for the main tunnel and for the Akalla-Häggvik interchange complex at the north end went to a joint venture of the local firm ÅF Infrastructure A.B. and what is now AECOM, with corporate headquarters in Los Angeles.
To target the bypass design contracts, ÅF considered the medium-sized, U.K.-based firm Scott Wilson Kirkpatrick Ltd. to be a complementary partner, says Jenny Johansson, ÅF’s manager of large projects. The companies shared transportation infrastructure expertise but lacked scale to bid independently. Since then, however, ÅF has grown to around 9,000 staff, while successive acquisitions have left Scott Wilson an outpost of the immense AECOM.
A requirement that the project’s owner, designers and contractors collaboratively use 3D modeling “was written into the contract, even though, at the time, it wasn’t fully understood what was entailed,” says John Forshaw, technical director at AECOM, Glasgow, Scotland. BIM was still in its infrastructure infancy in 2011 and represented a pioneering step for the AECOM team.
BIM also was new for ÅF’s infrastructure engineers, says Johansson. “It was difficult to be prepared, but we had expertise from the [building] side,” she adds. “It was new to the client, as well.”
AECOM-ÅF and Trafikverket developed a strategy to share data among the teams of various disciplines spread around the U.K., Sweden, Poland and elsewhere, using both the Swedish and English languages. To achieve information mobility, they chose Bentley Systems’ ProjectWise software package, which allows all the teams to work from the same models.
For the construction phase, “we tried to leave as much [design] as possible to the contractors,” says project director Brantmark. Trafikverket is generally responsible for the detail design of the tunnels and underground work. It is procuring the interchanges and concrete cut-and-cover tunnels through design-build contracts.
Bids for the owner-designed tunneling were largely based on 3D models. But for some complicated details, “we also had situations where we had to add traditional drawings,” says Trafikerket’s Niland. “Contractors [generally] had to be educated and told what was coming,” AECOM’s Forshaw adds. “Some contractors had better comprehension than others, but they are all coming round.”
On bids for the design-build contracts, “we pointed out all our [requirements] with 3D models and described all the [existing] conditions in 3D,” says Niland. Trafikverket then asked the contractors to continue designing digitally, but 40% to 50% of them “were a little afraid” and worked conventionally, he adds.
For the Kungens Kurva interchange design-build bid, Skanska Sverige A.B. received digital information, but “we chose not to do a 3D model … it was quite expensive,” says design manager Christian Söderkvist. Facing tough competition, the firm kept costs to a minimum, he explains. He estimates designing in 3D to be 20% to 25% more costly than the traditional approach.
Skanska won the $152-million design-build contract, which includes a large bridge and a 350-m open trough that leads to a 300-m cut-and-cover tunnel into the bypass. The contractor is handling the project’s concrete and geological design work and has the local firm SWECO A.B. doing the rest, says Söderkvist.
Almost Everything Is 3D
“Now, we are doing almost everything in 3D,” says Söderkvist. But hitting snags in modeling rebar, “we chose to do regular drawing,” he adds. Skanska design teams are using various software packages, including AutoCAD Civil 3D, Trimble Novapoint, Bentley Microstation and StruSoft Impact. “We mostly look at it on [Autodesk] Navisworks,” says Söderkvist.
Of the job’s subcontractors, “some could handle 3D already and some couldn’t,” says Söderkvist. Because of the need to wear gloves in Sweden’s cold winters, “concrete workers didn’t want to use iPads,” he explains. They are working with drawings.
“This is the first 100% 3D project I’ve worked on,” says Söderkvist. He has many years of 3D modeling experiences, “but it’s come a long way. We can now plan the whole project in 3D,” he says.
For the contractor on the Häggvik job at the other end of the bypass, digital procurement “was much more complicated” than the conventional approach, says Maria Christiansson, NCC’s design manager. “Not everybody could read the models. Some subcontractors had never seen a model.”
The $88-million Häggvik interchange contract includes a roughly 250-m-long cut-and-cover tunnel and five bridges, from 20 m to 200 m long. Work involves shifting 230,000 cu m of soil and 320,00 cu m of rock and pouring 29,000 cu m of concrete, says Paul-Anders Quist, NCC’s project manager.
To handle the bulk of the structural design, NCC recruited local firm ELU Konsult A.B., partly because of its experience with 3D design, says Christiansson. ELU is using Tekla design software and exporting models to Navisworks for review. All key files are exported to the ProjectWise platform, allowing all project participants to share information. It’s the place “where you collect everything that’s important,” she adds. Setting up design in 3D “will cost a little more initially,” says Christiansson. But she adds that, by providing improved quality and better change control, “my guess is that, in 10 years, everyone will use 3D models as the normal way of working.”
Trafikverket began awarding contracts for access routes and other preparatory work in mid-2014 and signed the first main tunnel contract a year later.
To encourage competition from local and international contractors, the authority divided the civil work for the tunnel into six contracts of various sizes. Several more contracts covered the six interchanges and the concrete cut-and-cover tunnels at various locations. “We got very good competition. Prices were as expected,” says Brantmark.
With only two small interchanges and one relatively short cut-and-cover tunnel still to be procured, Trafikverket has awarded $1.4 billion of work covering the rest of the major civil construction.
Six tunneling contracts for approximately 18 km of rock tunnel have been signed for about $990 million total. Of the six surface interchanges, two have yet to be awarded and four are under construction in design-build contracts, totalling $335 million.
Among the tunnel bidders, the biggest winners are Italy’s Rome-based Viannini Lavori SpA and Cooperativa Muratori e Cementisti di Ravenna. In a joint venture, they secured both tunnel contracts on Lovön Island. The contracts include some 7 km of tunnel valued at $422 million.
Units of Switzerland-based Implenia Generalunternehmung A.G. have the two contracts farther north, totalling 5.3 km for $308 million. Subterra A.S. of the Czech Republic is handling the southernmost 4.3 km of tunnel for $209 million. The final 1.4 km of main tunnel in the north, at Alkalla, is being formed by the local subsidiary of Austria’s Strabag S.E. under a $53-million contract.
Contractors on the bypass are moving up the BIM learning curve, but “many people still want to have drawings. They are more familiar with that kind of work,” says NCC’s Quist.
While the construction teams grapple with the new digital culture, old-fashioned logistics remain challenging, he says. “We have 100,000 cars passing around the site every day, and we need to [reroute] the traffic 10 to 11 times during the project.”