Fernando Vara; Project Director ACCIONA Ghella Joint Venture. Oslo, Norway
ACCIONA Ghella Joint Venture is commissioned by the Norwegian National Railway Administration (Bane NOR) to construct the main part of the Follo Line tunnel (EPC TBM). The tunnel will be the most significant part of the project, including two 20 km separate single-track twin tunnels. AGJV will construct 37 km of the tunnels by using four Tunnel Boring Machines (TBMs). What really makes this project probably iconic in the world is the logistical challenge of having the four TBMs starting in the same site location, compared with the typical two TBMS from each end configuration. The design of all the installations in the same location, has been a great challenge and the design achieved was a robust, compact and ready for 24/7 works under extreme winter conditions (-25º C) solution, that really has transformed a Surface challenge into an underground solution.
The Follo Line Project is currently the largest transport project in Norway. The project consists of a 22 km new double track railway line between Oslo Central Station and the new station at Ski, south of Oslo. ACCIONA Ghella Joint Venture will construct the main part of the 20 km long tunnel, which will be Scandinavia’s longest when it is finalized at the end 2021.
The Follo Line will form the core part of InterCity development south of Oslo and is commissioned by the Norwegian National Railway Administration (Bane NOR). The project consists of several EPC-contracts, in which the construction of the tunnels with TBMs is the most extensive. Installation of railway systems is also a part of the project, which will be completed in 2021.The tunnel contract has an approx. value of 8.7 billion NOK (1 billion euro).
- 37.000 ml TBM tunnel.
- 9 M tons of rock
- 140.000 concrete segments
- 1 M m³ of concrete
- 350 km of auxiliary pipes
- 1,000 workers peak
- More than 25 nationalities
The configuration of the area where the project was settled is an approximately 200,000 m² of platform, close the exit 26 of the E-6, and it includes the area for the spoil. As part of AGJV scope, it was necessary to excavate the transport and auxiliary tunnels and assembly caverns where the machines were going to be assembled. This activity was contemporary with the execution of the civil works for the factories, auxiliary installations, and TBM assembly.
The first complex task was to define and integrate the whole number of factories and installations that where needed, assuming that the time factor was critical. The contract was signed on 23rd March 2015, and the land was provided by Bane NOR on June 2015. The target schedule that AGJV settled was to start boring with the first TBM by September 2016, and the fourth and last one, by December 2016.
In order to achieve that aggressive schedule, AGJV design team (ACCIONA Ingenieria is the design company for the Follo Line EPC TBM project) worked very hard on the first 6 months of the project with all different AGJV production teams, till a final compact solution was defined and agreed between all. Finally, four different areas or platforms were established and would include all the factories and auxiliary installations: precast factories, spoil area, portals (lower area) and auxiliary tunnels area. All four areas were linked and integrated from a logistical point of view and final result was a very compact and efficient industrial/production “city”. A detailed description of those areas is developed in the next sections.
On the top of the challenge of design, procurement, preassembly on factory, disassembly, transport and final assembly on site of the four TBMs, in order to start the excavation of the tunnels with enough time slack, it was needed to have around 2,500 precast concrete rings minimum storage on site, so the precast factories had to be assembled and start the production months well in advance of the TBMs.
After some months of analysis and evaluation of what was designed during the tender process by ACCIONA and Ghella and what the new challenges and reality of the area provided, the first critical decision taken was to reduce from 4 precast factories, as previously agreed, to 3.
That decision was based on an optimization on the area for storage segments, assuming that with 3 factories and with time enough for starting the precast rings production in advance, the risk of not having rings enough for the TBMs was controlled and to increase storage capacity was more critical.
The second area that required intensive analysis and different solutions till achievement of the final optimized one, was the spoil shed, where the material excavated from the TBMs was going to be managed, and the crushing plant area for the production of the aggregates from the excavated rock. The spoil area had to be covered to allow working during winter time and night time, and integrated into the crushing plant area. Final solution was a massive shed covering the spoil, where the conveyor belts would be integrated and aligned, and a second shed for the storage of crushed aggregates produced by the crushing plant adjacent to it.
That integrated solution included a surrounding wide transit road for dumpers and road trucks, as both would be needed on different stages of the project.
Both the precast and spoil area were placed at level 169. The adit tunnel entrance, were the access to the main tunnels was placed, was at level 150. This difference of level was another challenge in terms of logistic optimization for the rest of the installations. Final design of the lower level was integrated in the confined space that the excavated portal area created, plus the tunnels access and necessary wide logistical roads. In this area the grouting plants, water treatment plant, substations, workshops and warehouses were finally allocated.
2.4.Auxiliary tunnel and assembly caverns
The fourth key area of the project were the auxiliary tunnels and assembly caverns. This area had the challenge of combining the intensive traffic that the vehicles getting into the tunnel were producing and the allocation of all tunnel auxiliary installations (ventilation, pipes, electrical cables and conveyors).
Two assembly caverns, located North and South to the adit access tunnels were designed for the assembly and launch areas for the TBMs, so it had to be big enough and at the same time be integrated into the final permanent tunnel design. Final dimension of the caverns were 35x25x50 m.
On each cavern 2 TBMS were assembled at the same time, and a jacking crane system was selected as the most compacted and polyvalent lifting equipment for that kind of confined space and complex assembly operation.
The integration and coordination of all the equipment installed into the four main areas previously described above, had been one of the key elements and success factors on the EPC TBM Follo Line project. On the top of the described areas, a common “construction green” area, including offices, barracks for 450 workers and a 24 h canteen, was assembled close to the site for the white and blue collars.
As a final general comment, all the design has taken into account the extreme weather conditions (-25º C) that the site area could suffer during winter time, (full covered conveyors, heating cable on asphalt, heated pipes, etc.).
On the following section, a summary of the main equipment and auxiliary plants is presented.
3.Main plant and equipment
3.1.Precast factories, batching plants and cranes
AGJV built a large concrete segment factory at the construction site to supply concrete precast elements continuously to the TBMs. The entire three factory area was about 20,000 m2 and had three production lines, batching plants and other auxiliary installations.
Seven concrete segments were needed in order to assemble one complete tunnel ring. The factory was planned to produce nearly 20,000 complete rings, or 140,000 concrete elements, in addition 20,000 invert elements.
Facts about concrete segments (universal ring type):
- A complete tunnel ring weights 51.6 tons and consists of seven concrete segments, in addition to one invert segment
- Each ring is 1.8 m wide, 9.55 m high and 40 cm thick
- Each ring consists of 32 parts, including elements, gaskets and pipes
Each of the temporary precast factory was assembled on site and included:
- 3 carousel: each carousel included 6 set of 8 molds. Total 48 molds (Segment and invert segment)
- Power installed and pumps → 129 KWs
- 1 curing chamber → 700 KW
- Water requirement: 400 l/h
For pouring the concrete a set of 3 batching plants was procured and installed integrated with the precast factory.
Main batching plant components:
- Model: SIMEN BT 75
- Production: 60 m³/h
- Total capacity for storage: 200 m3 for sand storage.
- 3 units per plant
- Dimension: Diameter 3.5 mts x Length 8.5 mts.
- Cement storage capacity silos: 70 m³ (approx. 95 ton)
- Silica storage capacity silos: 70 m³ (approx. 50 ton)
- Polarmatic heating units for concrete production under winter conditions (hot water and sand heating).
All the segments, and auxiliary material inside the factories have been lifted by a group of different cranes, as described below:
- 3 Segment external storage gantry cranes, 4×10 ton, 30 m span, 185 kW.
- 3 Demolding overhead cranes, 2×8 ton, 21 m span, 25 kW.
- 3 Pre-storage overhead crane, 4×10 ton, 15 m span, 60 kW.
- 2 reinforce workshop overhead crane, 1,3,2 ton, 26 m span, 8 kW.
During the excavation of the tunnel, between 9 and 10 million tons of rock were excavated. Some of this was reused in concrete production, while some was stored near the construction site.
The rock material excavated by the TBMs that has been selected as valid for the aggregates production, has been processed through a combination of crushing plants, which main characteristics are:
- Groups of crushing and screening Metso for reduction to gravels and sands.
- Two shredding groups LT300D and LT7150B, one mobile sieve ST 2.8 and one stationary CVB 202 and a sand treatment group.
The flowchart of this installation was, in summary, the following:
The feed was 0-100 of granitic rock. This 0-100 undergoes a cleaning process on an ST 2.8 screen which took advantage of size 20-80mm. This 20-80 was reduced in closed circuit to 0-25mm by means of a cone crusher on tracks LT330D. To obtain an excellent coefficient of form all sizes larger than 6 mm were processed in a vertical axis mill on LT7150B tracks. All 0-25mm already with excellent coefficient of form was classified in a stationary screen CVB 202 with washing to obtain gravel washed 12-25mm, 6-12mm. The resulting 0-6mm was taken to a hydrocyclone sand treatment group, thickening tank and filter press to achieve the quality. The production had to stop due to the mineral combination in parts of the material. Phyrrotite in combination with too high values of sulfur.
All the material excavated by the TBMs was transported to the spoil shed via a complex conveyor belt system. This conveyors had different sections and belts widths depending on the areas of the tunnel they are and could transport in some areas the full excavation of the four TBMs. The capacity of the conveyors varied from 850 t/h to 2,000 t/h, belt widths from 1,000 mm to 1,200 mm, max. speed belt 3m/s, and the installed power of the head end drive, booster drive and tail end drive went from 945 kW, to 315 kW and 250 kW respectively.
On TBM excavation methodology, it is needed to fill the gap between the external precast ring diameter and the TBM excavation one with morter.
On the Follo Line EPC TBM Project, AGJV has chosen the bi-component morter solution. Basically is a combination of 2 elements: Component A is a colloidal suspension cement based, with other hydraulic conglomerates, and Component B is an accelerator (sodium silicate).
The grouting plants chosen for the mixed and production of the bi-component have been 2 units.
Each Unit Plant consisted in:
- 1 Grout Mixer Unit (2 x 20 m³/h)
- 6 Vertical Monolithic Silos 85 m³
- 1 Agitator (2 x 6 m³ tanks)
- 1 Transfer Pump for A Component (2 x 20 m³/h)
- 1 Control Room for the 2 Mixing Plants.
- 4 Transfer Pumps for B Component
The auxiliary equipment in the plants were:
Mixer → 2,5 m³, 2,000 l/min, 15 kW
Silicates installations → 8 container of 25 m³ each one.
3.5.Water Treatment Plant
All the water pumped form the caverns to the surface was treated in a water treatment plant specifically designed to treat the kind of water that a construction project generates. The contract is very strict in terms of water discharges to the sewage network and water quality levels, so the robustness of the plant was critical.
The main characteristics of the water treatment plant were:
- Total treatment capacity: 216 m3/h
- Waste water containing on average 15 g/l of TSS
- Power install: 223 kW
- Effective working hours : 24
- Oil And grease limit: average 2,000 l/day
- PH limit: 4 to 12
- Buffer and storage waste water tanks
- Automatic flocculent station
- Decanter cylinder tank FB7000V-WDR
The quality limits for the final discharge water were:
- pH limit: 6.5 – 8.5
- Solids contents: 25 mg/l
- Oil and grease limit: not visible
Ventilation of the main and auxiliary tunnels was another very complex design solution, as the site configuration was more similar to an operation mining area.
The final solution included main fans for the TBM tunnels and auxiliary jet fans for the rest tunnels.
Main characteristics of the equipment installed:
- Main Fans:
- Model: ZITRON ZVN 1-20/315-4
- Reversibility: Unidirectional
- 4 units in a principals tunnels.
- Power: 315 kW
- Diameter: 2000 mm
- Flow: 68 m3/s
- Jet fans:
- 24 units in the two adits.
- Adit South → 7 pairs
- Adit North → 5 pairs
- Power: 41 kW
Good design in advance, smart ideas, previous experience and lessons learnt from other similar projects that ACCIONA and Ghella were involved around the world, have been the key factor for an achievement of a very compact, robust and 24/7 workable solution.
But as important as the design of the whole site, the logistic functionality of the day to day operations is another key element in this kind of continuous production sites.
The logistic team coordinated the daily internal and external deliveries on site, warehouse, workers shifts on barracks and their continuous rotation, among other activities.
The delivery to the TBMs of workers, materials and segments was one of the main activities. AGJV optimized the traffic on the tunnels by the way of using multiservice vehicles (MSVs). These special transport vehicles allowed to have both ways of traffic into the TBM tunnels with no interruption, as they are narrower that standard vehicles.
Different type of special vehicles have been procured on the project: men rider (allows to transport 28 people), segment vehicles (2 complete precast rings can be delivered at the same time) and special platforms for rescue chambers, materials, ventilation, etc.
Main characteristics of those vehicles:
- MSV for RINGS
- 5 units
- Model: MSV 130-4-1900
- Power: 405 KW
- Service: Each vehicle carries two complete rings.
- Quadruple Multiservice Vehicle, 8*18*18
- Turning radius: 15 m.
- Dimensions: 2100 x 3306 x 43,615 mm
- Weight unloaded: 48,000 kg
- Maxi vehicle weight: 172,000 kg
- Maxi speed with load on flat ground = 17 km/h
- Maxi speed with load in maxi slope (10%) = 10 km/h
- MSV AUXILIARY
- 11 units
- Power: 245 kw
- Weight unloaded: 17.000 kg
- Max capacity(payload): 21 tn
- Crew transport → 5 units. 21.×1.981×3.940 mm 18.000 kg
- Rescue chamber → 4 units. 24.198×1.981×3.940 mm. 18.500 kg
- Duct cassett ventilation → 2 unit. 23.894×1.981×3.940mm. 18.500 kg
For the excavation of the 36 km. of tunnels, ACCIONA Ghella Joint Venture procured four brand new tunnel boring machines (TBMs) to Herrenknecht, a worldwide German TBM specialized company. The main characteristics of the machines are:
- Adapted to high rock strength. Bane Nor input based on Norwegian experience
- 71 Cutter rings 19” on 70 tracks
- Heavy structure, stiff support
- Diameter machine/tunnel: 9.96 m/8.75m
- Length of machines: 150 m
- Weight: 2,400 tons
- Installed Power: 6,200 kW.
- Main bearing size increased to ø 6.6 m
The TBMs were designed, manufactured, preassembled and commissioned at Germany (Herrenknecht facilities at Schwanau) previously to their transport to the job site. This works took one year for the 4 TBMs (the contract signature took place on 23rd March 2015). This fantastic production process allowed AGJV to gain some float for the start of the works.
The TBMs 1 and 2, which were facing towards Oslo direction (North), started excavation on September 2016 and on October. The breakthrough of both TBMs took place on 11th September 2018.
The TBMs 3 and 4, which were facing towards Ski direction (South), started excavation on November and December 2016 and achieved both breakthrough on 26th February 2019.
In the table below the main production excavation, dates and values are summarized:
The previous figures have to be interpreted into the following context:
- Pregrouting affects normal TBM exca-vation, as no excavation is possible dur-ing this activity.
- In the extremely hard Norwegian rock, the TBMs cutters consumption is mas-sive, requiring lots of TBMs operators’ entrance into the cutter head chamber for checking cutters status and change cut-ters.
Even with these two factors taken into account, the TBMs have achieved the expected TBM production rates (between 14 and 15 m a day), so it proves that the TBM tunnel methodology is more than capable to be used for excavation of tunnels in tunnel, compared with standard drill&blast methodology.
Although the majority of the contract relates to the excavation of the 36 km of tunnel, there are still a large number of activities to be completed before the end of the contractual period in April 2021.
The main tasks are:
- Cladding of the connecting galleries be-tween the two main tunnels.
- Civil engineering works for the railway system installations.
- Positioning of lateral walkway (precast concrete).
- Concreting of track beams.
- Assembly of sleepers, rails and ballast-less track.
- Installation of railway system installa-tions (transformers, ventilation, catenary, cables, etc.) in connecting galleries and main tunnels.
The Follo Line EPC TBM project is unique especially due to the size and the use of four TBMs from the same construction site.
But as previously described, ACCIONA Ghella Joint Venture is an international team (1,000 employees and more than 25 nationalities) with plenty of Norwegian subcontractors that has been capable to achieve ahead of schedule a complete design, procure and assembly program of all the equipment and facilities on site. One of the main reasons for it has been the capacity of the ACCIONA Ghella Joint Venture Team to bring to the table innovative techniques and solutions coming from their international experience based on previous similar projects around the world.
The second main reason has been the good cooperation with the client (Bane NOR). Regular meetings to inform and decide have been important, in addition to good discussion.
As a consequence of it, all four TBMs started excavation ahead of the contractual schedule, the production at the large precast factory at the site has been reliable with good quality and AGJV has excavated more than 18 kilometres of tunnel on time, delivering quality, safety, innovation and experience.
There is still a lot to do, and big challenges will come, but the Follo Line EPC TBM team is very proud of having transformed a surface challenge into an underground solution.
Special thanks to Jacobo Arnanz (AGJV Construction Manager), Andrés Merino y Alberto Busto (AGJV Tunnel Managers), Jesus Espinosa (Design Manager) and all AGJV team for their fantastic and professional work they have done at the Follo Line EPC TBM Project.