Lötschberg plans full rail baseline finish 21 Mar 2019

The Bern–Lötschberg–Simplon rail company in Switzerland, now known as BLS AG, is preparing to submit plans to the Swiss Federal Office of Transport in early April to fully complete both tubes of the Lötschberg Base Tunnel that opened 12 years ago but with only a single operation tube, which has quickly become a bottleneck to growing rail freight across the Alps. A section of about 7km at the north end of the west tube remains to be excavated and most of the excavated parts of the west tunnel are to be fitted out for operation (Fig 1). A new crossover is also to be excavated and equipped.

Planning underway to complete the Lötschberg Base Tunnel

After submitting the plans, BLS Project Manager for Lötschberg, Stefan Irngartinger told TunnelTalk that the rail company will then carry out detailed design and procurement planning towards receiving approval for the works by mid-2020, a call for tenders in 2021, and for construction to start in 2021/2022 and be completed by end of 2028.

The Lötschberg Base Tunnel is one of the family of long trans-Alp rail links and the first in this century to come into operation, in mid-2007, although not fully. The 34.6km long base tunnel was designed and excavated as a twin tube facility with linking cross passages, but was commissioned with only the east tunnel fully completed and operational. Much of the west tube was excavated and structurally built but only a short section at the south end was fully equipped. As a result, the Lötschberg tunnel runs over about 20km, or the majority of its length, in a bottleneck single tube that restricts capacity.

Since its commissioning, the plan has been to fully complete the Lötschberg link when funding becomes available. Funding to fully complete the Alpine strategic rail link over its entire length is coming from the Swiss Government as part of its large Strategic Expansion Programme STEP programme of rail investment for the country. The budget for the completion of all planning and construction works for Lötschberg is estimated at CHF 920 million (about US$922 million) in 2015 prices and has a margin for change allowance of +/- 25%.

Layout of current operating tunnel and future completion works

Phase 2 build out

When it came into commercial operation in mid-2007, the Lötschberg Base Tunnel was the longest tunnel in Switzerland and the third longest in the world. Developed on the Lötschberg-Simplon rail axis, it was the forerunner to subsequent Trans-Alpine rail tunnels the Gotthard and Ceneri tunnels in Switzerland, and the Brenner Base Line, which is under construction between Austria and Italy.

Main construction for Lötschberg was mainly by drill+blast. The geology exhibitied a north-south split with flysch, marly limestone, slate and sandstone at the north end, granite in the middle and, schists, gneiss, amphibolites and sediments in the south. Excavation progressed from the north and south portals and three intermediate adits with 80% completed by drill+blast on headings of 65m2 to 78m2. The balance, at the south end, was completed by 9.43m diameter TBMs. Having started excavation in 1999, the tunnelling to that stage was completed by 2005 and fit-out followed to open the link using a single tube in part for bi-directional traffic.

Lötschberg opened in 2007 but as a single rather than twin tunnel facility

Since opening in 2007, traffic increased with the Lötschberg axis to carry about half of Trans-Alpine freight transport. By 2017, the axis took 35.7 million gross tonne of rail freight. Daily, the base tunnel, despite the bottleneck constraints, accommodates up to 60 freight trains plus about 50 passenger trains.

Phase 2 build out

In 2014, the electorate, when asked by the Swiss Government, voted by majority to fund the further completion of Lötschberg, allowing preparations for planning to get underway. The works will include both major tunnel construction and equipment fit-out in the west tunnel but also handling complicated logistics as trains continue to pass through the operational east tunnel.

Irngartinger told TunnelTalk: “The logistical concepts for constructing the tunnel have to respect the rescue and evacuation processes for the operated tunnel, where the west tunnel will be both a construction site and also an emergency exit for the operating east tunnel. In case of emergency, the construction site has to be cleared within minutes so that the unfinished tunnel is accessible for rescue teams.”

New construction will include cross-junction works

BLS began planning work for the project in 2016 through its rail infrastructure unit BLS Netz. The first phase of work will involve completing the inverts as well as track installation and M&E fit-out in the constructed but unequipped tunnel. The plans are being developed in line with finance approved through the national STEP 2025 programme, following which the STEP 2035 programme will cover the further costs and works, including last excavation and fit-out.

The initial proposals for the STEP 2035 programme, covering a range of proposed rail project improvements across Switzerland, have been given a total budget of about CHF 11.9 billion (about US$11.92 billion. In mid-2018, the Swiss Government included the second phase of the completion works for the Lötschberg rail corridor in the STEP 2035 plan. Earlier this month, the Parliament proposed to increase the overall budget for the entire programme to CHF 12.8 billion (US$12.83 billion) to accommodate other projects. Approval of this revision is expected later in 2019.

The works will focus mostly on the west tunnel as the east tube was fully excavated and fitted-out for operation. The west tunnel, instead, was excavated but only fully structurally completed and equipped along its first 14km, at the south end. The remaining part of the west tunnel that was excavated has a primary lining and will require instalation of the invert and final lining, and then be fitted-out with tracks and M&E equipment, to be completed. The unfinished portion of the west tunnel, in the meantime, has provided maintenance access as well as rescue and evacuation routes, Irngartinger explained.

Section view of the planned cross-junction works

Maintenance access and evacuation routes from the operating east tunnel for the 7km unexcavated part of the west tunnel are provided through the 9.5km Kandertal exploratory tunnel running on the other side of the east tube (Fig 1). The exploratory tunnel was excavated by a 5m diameter TBM in the mid-1990s.

The Lötschberg rail corridor also includes the 2.6km long twin tube Engstlige Tunnel immediately to the north of the base tunnel. Its twin tubes were built by cut-and-cover but only its east tunnel was equipped for operation. As a consequence the entire Lötschberg rail corridor has been operating with only single track over a length of almost 23km since it opened, creating continued logistical challenges for running trains. Current planning includes track and M&E equipment through the Engstlige west tunnel.

Completion challenges

Irngartinger explained to TunnelTalk that the main construction challenges in the completion works for Lötschberg Base Tunnel involves two key factors: managing new excavations in the west tunnel and examining the condition and providing support to the adjacent, and operating, east tunnel.

Finishing works of the west tunnel could be underway by 2021-22

The excavation method for the majority of the tunnelling needed is yet to be decided, he said, but adds that it would probably be drill+blast. The works will involve excavation of new tunnel sections and caverns close to the operating east tunnel; analysing the stresses and deformations of the inner lining in the east tunnel and comparing the data with those of the unfinished west tunnel; and, matching infrastructure across the tunnels, noting that some components will be nearing their lifetime usefulness. Everything will be have to be completed while train services continue. A key part of the construction and excavations adjacent to the east tunnel involve backfilling an existing crossover tunnel and to create a new, longer, crossover in its place capable of carrying faster trains.

Consultants advising BLS Netz on the completion of Lötschberg rail corridor include SRP Ingenieur AG, Emch+Berger, IUB Engineering, PRA Ingenieurs Conseils SA, BG and HBI.

Other tunnel improvement works being performed by BLS Netz on the Lötschberg corridor involve refurbishment by Marti Tunnelbau of the Lötschberg-Schieteltunnel, higher in the mountains. The 14.6km long tunnel was built about a hundred years ago and was previously known as the Lötschberg Tunnel until the longer base tunnel was constructed.