For the last few decades, Norway has been striving to better knit together key stretches of the road network that hugs its fjords on the west coast. The strategic vision is to save time and boost regional economies, and to that end a variety of construction methods have been employed to cross the straits, such as bridges and subsea tunnels – the latest of which is the Ryfast scheme under construction near Stavanger.
The Ryfast link will be 19.5km long, built almost entirely underground, and will establish the Rv13 road as an all weather link between Stavanger and Ryfylke region to the east. The fixed link will replace the current ferry connection.
Ryfast comprises two tunnels: Hundvåg Tunnel, which will weave out from under central Stavanger to surface at Hundvåg island; and, Ryfylke Tunnel, running on from the island for about triple the distance and depth below sea level of Hundvåg Tunnel, to emerge at Solbakk near Tau, in Rogaland county.
Yet, for all its size, Ryfast is only a branch off the west coast’s main trunk road – the E39. They will be connect at another new tunnel – Eiganes Tunnel – a shorter, new landonly link sits on the main highway.
The national roads authority, Vegvesen, is constructing the three tunnels as part of the same scheme, which was approved by the Norwegian Parliament in 2012, and is to open to traffic by 2019.
In addition to improving regional links, the scheme will also help reduce traffic congestion in Stavanger, says Ryfast-Eiganes project manager, Gunnar Eiterjord.
Subsea road tunnels have been a key feature of the transport improvements made along the E39 from Kristiansand to Trondheim, and more are planned, says the route’s project manager, Olav Egil Ellevset.
One large project is well ahead in planning – the 25.5km long Rogfast scheme, which would be Vegvesen’s longest subsea road tunnel.
If parliamentary approval were to be received this year, construction might start around 2015, the roads authority proposes.
If so, then the overlapping construction schedules of Ryfast and Rogfast could mean Stavanger becomes an even greater tunnelling hotspot later this decade.
Ryfast and Eiganes tunnels
Consisting of the Ryfylke and Hundvåg tunnels, which are 14.3km and 5.5km long, respectively, the NOK 6.2bn (US 1bn) Ryfast strait crossing is a twin tube link in both sections. There the similarity ends, for the longer of the two is the narrower, and will take less than half of the traffic, but will go much deeper.
Ryfast’s geology comprises gneiss and phyllite, and Eiterjord notes that small leaks were experienced when tunnelling through phyllite in a previous scheme, Rennfast, which included the Mastra Fjord tunnel near Stavanger.
There is also phyllite in the Stavanger area of the 3.7km-long Eiganes Tunnel, which is budgeted at NOK 2.5bn (USD 405M). While Eiganes is far shorter than Ryfast overall, and being constructed totally on the mainland, it is budgeted to be just over double the cost per kilometre.
Eiganes is much more of an urban route than the Ryfast tunnels, and its challenges include: the built environment; underground ramps and connections to the existing road network; the highest forecast traffic volumes of all the tunnels; and, therefore, it has large twin tubes of the same size as Hundvåg. Eiterjord notes that parts of the route have only 15m to 25m cover.
The balance of Eiganes’ project finance structure is also notably different to Ryfast’s: the state will fund 49 per cent of Eiganes; but Ryfast only gets 14 per cent from central government plus 6 per cent from local government, the city and business. The balance of funding for both projects is to be paid through road toll charges – and so would make Ryfast the most expensive road link for road users in Norway, notes Vegvesen. The main consultant of the scheme is Norconsult.
Ryfylke Tunnel
Ryfylke Tunnel is the main strait crossing link on Ryfast, and stretches from Hundvåg to Solbakk, passing below the island of Hidle on the way. Until recently, it was called Solbakk Tunnel.
Two contract packages have been awarded for construction of Ryfylke Tunnel, and Hidle island marks the boundary between them – Contracts E02 and E03, which are 7.6km and 6.7km long, respectively, says Eiterjord. The tunnel is 290m below sea level at its deepest point, on Contract E02.
A JV of Swiss contractor Marti and its Icelandic subsidiary IAV was awarded Contract E02 tunnel and portal works in April 2013. Tunnelling on the NOK 1.3bn (USD 218.5M [excluding VAT]) contract began the following August.
Twin drives are being blasted from the Solbakk portal, driving westwards. By the beginning of 2014 the faces had each advanced approximately 500m, says Anne-Merete Gilje, Vegvesen’s project manager for Ryfast. From Solbakk, the tunnels will descend at inclines of 7.2 per cent to the lowest point of the link, below Hidle fjord, and from their will rise at 1.3 per cent grade towards the island.
The Contract E03 works will construct the Hidle to Hundvåg section of Ryfylke Tunnel, plus a small part of neighbouring Hundvåg Tunnel. Vegvesen signed the NKr 1.17bn (USD 196.6M [excl VAT]) contract with local firm AF Gruppen in July 2013, and the drill and blast drives were about to get underway in January, advancing eastwards from the Hundvåg portals. The vertical alignment has grades of 7.9 per cent and then easing to 2.7 per cent below Horge fjord towards Hidle, to meet the E02 drives.
Upon completion, Ryfylke twin tubes will have horseshoe-shaped, T8.5 finished profiles (8.5m wide at road level, and 4.6m clearance), each with two lanes for traffic. The tubes are to be connected every 250m by emergency access tunnels. Opposite every second exit will be a widened area for vehicles to stop.
Forecast traffic levels at the opening are 4,000 vehicles/ day, doubling by 2035. Below Hilde, the tunnel will be locally widened and have soft feature lighting on the walls to break up the monotony of the long journeys for drivers, says Vegvesen.
Hundvåg Tunnel
Traffic coming from Solbakk will emerge from Ryfylke Tunnel onto a short open stretch of road on Hundvåg island, next to Stavanger, and then quickly enter 5.5km-long Hundvåg Tunnel to complete the journey into the city.
Under Contract E03, AF Gruppen is also to construct the Hundvåg Tunnel’s portals as well as those for its main contract. However, the majority of Hundvåg Tunnel – almost, but not quite reaching E39 Eiganes Tunnel – is to be built in Contract E05, which was due to be awarded in late January, says Gilje.
Hundvåg Tunnel’s twin tubes will be constructed with T9.5 finished profiles (9.5m wide at road level, and 4.6m clearance), include access ramp tunnels near Buøy on the island, and descend to 95m below sea level. It will come out next to Gamlingen junction in the city, near the south end of E39 Eiganes Tunnel.
Like Eiganes Tunnel, among its design and construction challenges is the urban setting and, hence, sections with low overburden, notes Gilje.
Traffic levels in Hundvåg Tunnel are forecast at 10,000 vehicles/day initially, rising to vehicles/day after 16 years. The tunnel will relieve traffic on City Bridge, which links the island to Stavanger.
Eiganes Tunnel
Eiganes Tunnel will run from Tasta, at the northwest edge of the city, to just south of Gamlingen. It is to be mostly constructed under Contract E04, the bid deadline for which was mid-December 2013. Eiterjord says it will be the largest and most diverse contract on the entire scheme. Excavation is expected to start this Spring, adds Gilje.
Part of the works package also include, at Gamlingen, the south end of Hundvåg Tunnel, including the portals and short sections of tubes.
Eiganes Tunnel’s own twin tubes are the same size as those of Hundvåg Tunnel, but the volumes of traffic are forecast to be much higher – 20,000 vehicles/day at opening, rising to 35,000 vehicles/day by 2035.
Rogfast
Currently, the E39 highway is bottlenecked at Stavanger. After the congestion of traversing city roads, the journey onwards takes vehicles via a series of small islands, and short subsea tunnels, to reach the larger island of Rennesøy. Then, from there, a ferry shuttles from Mortavika across the Bokna fjord to Arsvågen, on the island of Vestre Bokn.
The subsea road tunnels are Mastra Fjord and Byr Fjord, which are the two key parts of the Rennfast scheme built in the early 1990s.
However, if Vegvesen’s latest plans go ahead, the route will be quieter after 2022, and the ferry gone, as the E39 is being re-routed to stretch north from closer to Stavanger. The colossal Rogfast fixed link is to take traffic across the fjord to Arsvågen.
Yet, in the 1990s, when Rennfast was being built, the idea of such a fixed link over such a deep and wide fjord as Bokna was thought "unrealistic in the foreseeable future," Ellevset told delegates at the latest Strait Crossings conference, held in Bergen last year.
But ongoing studies, drawing upon technological advances in tunnelling, brought a plan for a world recordbreaking length of subsea road tunnel.
And, at its deepest, the Rogfast tunnel would be 380m to 400m below sea level, even though the fjord goes much deeper. The feasibility design has been able to take advantage of the seabed profile created when the fjord was floor was carved in the Ice Age; there is a curved sill at the mouth of the fjord, and the tunnel alignment traces that path.
Usually, a subsea road tunnel has to compete against a bridge option to form a strait crossing on the Norwegian west coast. Not so at Bokna fjord – that is, until relatively recently.
Again, technological advances for bridges were the key. Construction technology had moved sufficiently ahead that, almost three years ago Vegvesen "saw that such bridges were possible," says Ellevset.
The competition was on, but didn’t last. Looking at a five-span suspension bridge with towers supported on floating pontoons, or platforms, Vegvesen realised it would be far too expensive – about three times the estimated cost of the tunnel. It was dropped in late 2012, leaving Rogfast as "a subsea tunnel project only," says Ellevset.
Tunnel concept
Vegvesen has settled on a twin tube tunnel concept, linked by cross passages, for Rogfast, project manager Tor Geir Espedal told the Strait Crossings conference. He said the estimated cost of the scheme is NOK 10.2bn (USD 1.64bn).
The tunnel route runs from near Harestad, in Randaberg, northwest of Stavanger, and passes below the fjord – passing the island of Kvitsøy – to surface near Arsvågen.
Geology along the alignment is complex. It is understood to comprise phyllite and mica schist near the Randaberg end but then, depending on the throw of the fault zone, may enter the Karmøy Ophiolite (gabbroic gneisses, hypabyssal rock types, volvanic rocks, sediments and dark, quartz-free ultramafic rock types) or Storheia Nappe (granitic and dioritic gneisses), or go right down to phyllite. However, further faults could lead to more variations in what may be met before the tunnel is in phyllite again at the Arsvågen end.
Onshore and offshore surveys are currently underway to supplement data already compiled by consultants Sintef and Cowi.
The deepest point of the tunnel alignment is about midway between Kvitsøy and Arsvågen – in the faulted area with the least known geology.
From there, the maximum slope is proposed to be seven per cent over a 3km-long section up to Arsvågen, and an additional climbing lane for vehicles might be included. But Espedal says design development, instead, might see the grade reduced to five per cent and the section made up to 1.5km longer.
Passing near Kvitsøy, the scheme will have a 4km-long access tunnel branching off to the island as a single tube from the main tunnels via a two-level interchange. The branch tunnel would house fire doors to protect the main tunnels.
Cross passages are planned at 1,250 to 1,500m centres for emergency vehicles, and for all vehicles every 4km. Emergency exits for passengers are to be no more than 125m apart when the gradient is five per cent or more.
Longitudinal ventilation is to use the piston effect of traffic moving the air mass, but airflow would be boosted by impulse fans.
Espedal says the Rogfast tunnels – planned as T10.5 cross-sections (10.5m wide at finished floor level) – might be bored rather than blasted following a tunnelling study that also considered using TBMs. Typically, Norwegian subsea road tunnels are excavated by drill and blast, and the method was looked in a feasibility study by Cowi and Sintef.
Sintef’s Eivind Grøv briefed the Strait Crossings conference on the study, particularly the possibilities for TBMs. Shield bores are considered able to offer benefits such as broadly greater tunnelling speed, reduced grouting, and lower excavation risks in weaker geological zones, but the method is estimated to be more expensive.
The study looked at boring 12.2m o.d. twin tubes by TBM, or a possibly a single, 19.6m o.d. tunnel. Various scenarios were examined with different numbers of TBMs to suit tunnelling sequences, risks and logistics.
It was concluded that tunnelling risk could be reduced by delaying cross passage construction until the main tunnels were finished.
Project funding for Rogfast is mostly based on tolls, similar to Ryfast. Traffic levels are forecast at 6,000 vehicles/day at opening, rising to 13,000 vehicles/day over 20 years, after which the tolls stop.
Future: tunnels and tolls
Aside from Rogfast, the next subsea tunnel contending for a spot on E39 is at the Vestnes-Otrøya strait crossing, one of two fixed links on the Møreaksen scheme to connect Molde and Alesund, in mid-Norway.
A final decision on whether the 15.5km long tunnel will proceed as the favoured option is expected this year, says Ellevset. The tunnel would be 330m below sea level at its deepest point.
At Halsa fjord, a subsea tunnel was previously the main option for a fixed link. Two tunnel alternatives were considered with lengths of 12km and 16km, respectively. But a suspension or floating bridge "has become more likely now," says Ellevset.
"So, for the E39 project," he says, "bridges will be the main focus for most of the remaining crossings due to the depths" at the fjords.
However, as noted at the Strait Crossings conference, other construction technologies are being explored, such as anchor-weighed or floating submerged tunnels for either full fjord crossings or as part of hybrid fixed link structures. Such ideas have been examined in feasibility studies to cross Sogne fjord, a tourist magnet for cruise ships.
While plans are made, however, there are fresh uncertainties surrounding the toll regime in future, following a change of government at the national election, in autumn 2013.
"We expect some change in the policies related to road tolls,"says Ellevset.
What certainty there is, though, is that Stavanger will become a busy centre for tunnelling in the near future.
