Uetliberg Tunnel: Waterproofing

Roland Förstler 1) Abstract: The western motorway bypass of Zürich actually under construction will fill one of the last gaps in the Swiss motorway network. The Uetliberg tunnel project is part of this bypass and consists of two 4.4 km long two-lane tunnels, a cut-and -cover section comprising the ventilation plant, gallery link and a gallery with a 80 m high shaft for the evacuation of the vitiated air. The waterproofing work is very demanding on all parties involved. The tunnels need in some places (ground water zone) water pressure containing waterproofing and in some places drained, non water pressure containing waterproofing. To prevent water infiltration from the pressure-containing section into the non pressure-containing section, the transition zones between the sections must also be sealed off against the rock. The water pressure-containing waterproofing system consists of a single, monitorable and injectable membrane layer with "Rückfallebene" (second defence line). The pressureless, drained waterproofing system is not designed for systematic injections. In both sections, injectable waterbars welded onto the membrane serve the purpose to enclose possible leakage zones. The invert/vault joints are sealed off with special waterbars and systematically injected. In order to ensure an as par as possible creaseless installation the closest possible to the substrate, the waterproofing membrane is fastened by VELCRO® system. The waterproofing system described in this paper has been developed by the project designer, main contractor and waterproofing subcontractor in close teamwork. This way it was possible to make fruitful use of all experience gathered in the course of the last years. Keywords: Project, sealing system, application methods. Outline Project • Overview • Characteristics, Milestones • Project participants Sealing System waterproofing membranes • Requirements • Substrate, Drainage system • Areas with/without water pressure • Compartments, joint details Application methods Costs /Conclusion

Uetliberg Tunnel

Introduction The motorway network in Switzerland is complete to a large extent. There however still exists a big bottleneck in the Zurich area. All north-south and east-west traffic passes more or less right through the middle of the city, not least to the great annoyance of our northern neighbours having to pass, right through the centre of the biggest

A51

Austria

N4.1.6

BernFrance

A1

Birmens-

LuzernItaly

Lake Zurich

A3Chur

Italy

Zurich

St. Gallen

AustriaGermanyA1

SchaffhausenGermany

Uetliberg tunnel

dorf

Gubrist tunnel

N4.1.5

N4

N20.1.4

A4

A1

N4.1.4

The Limmat

AirportKloten

start of constructionSpring 2001

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Swiss city on their 1000 to 2000 km journey to the Italian beach resorts for their annual holidays. This situation will change in 2010 when the western bypass of Zurich will be completed and linked to the already existing northern motorway ring. Several tunnels are being built for that at this time. One of these tunnel projects is the subject of this paper. However, the Uetliberg tunnel project is worth mentioning not only with respect to the excavation which, thanks to a proposal submitted by the contractors, is done using the most advanced method by means of a 14.10 -14.40 meters widening TBM equipped with undercutting technology.

TBM bore head, diamerter 14.10 -14.40 m Project Overview The project comprises two underground tunnels, one cut-and-cover section in the ground water zone with the ventilation control room, furthermore a temporarily canalised river crossing the project at a height of 20 m, a waste air gallery with an 80 m high vertical shaft and a 20 m high vitiated air chimney. The tunnel waterproofing must meet high requirements. Over a tunnel length of almost 10 km about 360'000 m2 of integral tunnel waterproofing membrane systems, partly containing water pressure and partly drained, not containing water pressure, are being installed. The waterproofing system in the ground water zone with presence of water pressure must not only form a tight seal towards the interior of the tunnel but also towards the surrounding ground. The reason for this is the specification not to disturb the original ground water situation i.e. not to drain the ground towards one or the other side. The main contractor for the tunnel as well as the waterproofing subcontractor having so far brilliantly achieved their tasks, this project is ideally suited to be presented in this paper.

Project Description The project comprises two parallel tubes, each about 4.4 km long. The tunnel falls with a gradient of about 1.6% from the Zürich South motorway interchange at Brunau to the Zürich West interchange at Filderen. The tunnel tubes are connected every 300 m by a pedestrian gallery and every 900 m by a gallery practicable by vehicles. The SOS niches are spaced 150 m apart. Portal stations are located at both the east and west part with control and machinery rooms. An

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underground ventilation facility is being built at Landikon in the Reppisch Valley. Three lane crossover points are built for the diverting traffic in the event of disturbance such as accidents, fire etc. The construction of the Uetliberg Tunnel will generate about 1.7 millions m3 of broken rock and debris. The portion of this muck, not used in the project, has to be removed by rail. Road transportation is not allowed. Consequently a conveyor was installed from the Landikon construction pit to the railway loading station in Filderen. The conveyor belt runs through a 550 m transportation tunnel, diameter 3.70 Meter, especially built for this purpose.

Characteristics

Excavated area • 143 – 160 m2

Volume of muck and spoil material • 1.7 million solid m3

Shotcrete • 137’000 m3

Concrete • 187’000 m3

Waterproofing membrane • 360’000 m2

Allowed time for shell construction • 6 years

Milestones Approval of the project by the Swiss Federal Roads Authority

• January 2000 Award of the tunnelling works

• September 2000 Start of the maintunnel works

• October 2000 End of shell construction

• End of 2006 Official opening of tunnel

• End of 2008 Project Participants Overall project and construction management

• Engineering Department of Canton Zürich • Office of Civil and Underground Engineering

Lockergesteinstrecke GjuchMolassestrecke EichholzLockergesteinstrecke DiebisMolassestrecke UetlibergLockergesteinstrecke Juchegg

210.00 m500.00 m

~~~~~

240.00 m2800.00 m

410.00 m

MoräneVerschwämmte MoräneSandsteinMergelLehm

GrundwasserspiegelLeitniveaus

12345

Konventionell (Bagger, Stahleinbau etc.)Sprengtechnischer VortriebKonventionell (Bagger, Stahleinbau etc.)Mechanischer Vortrieb (Pilot-TBM+ TBEKonventionell (Bagger, Stahleinbau etc.)

+400

+500

+600

+700

+800 UETLIBERG

ETTENBERG

Tagbaustrecke Reppischtal mit Lüftungszentrale

Portalstation Wannenboden

Abluftkamin Eichholz

Portalstation Gänziloo

43 5 1 2

Eichholztunnel

Uetlibergtunnel

)

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• National Highway Dept, Zürich/CH Project design and construction supervision

Tunnelling and overall co-ordination • Amberg Engineering Ltd. Regensdorf •

Cut and cover sections • Fiez AG, civil engineers, Zürich • Henauer + Gugger AG, engineering company, Zürich • Hans Eichenberger AG, engineers, Zürich

Construction Joint Venture “Uetli”, led by Zschokke Locher, Zürich

• Murer AG Erstfeld • Prader AG, Tunneling Zürich • CSC Bauunternehmung AG, Construction Zürich • Wayss & Freytag, Munich/Frankfurt • Alpine Mayreder Bau GmbH, Salzburg_Wals • ZüblinSchlittlerSpaltenstein Bau AG; Zürich

Subcontractor Flexible waterproofing

• SikaBau AG, Zürich Waterproofing In the Ettenberg Tunnel zone, in the loose soil zones Uetliberg and in the zone of the waste air installation, the tunnel waterproofing is executed in different ways i.e. integral membrane system containing water pressure in loose soil and molasse ground water zones and drained integral membrane system containing no water pressure in the "dry" molasse zones. Two and three millimetre thick polymer waterproofing membranes on synthetic fleece and/or drainage mats are used. Requirement regarding degree of watertightness The watertightness for the tunnel waterproofing is specified according to STUVA DK2 as follows: - Moisture definition for inner soffit: Almost dry - Application field: Tunnel aereas and emergency exits - The inner soffit my only show a few failing spots (e.g. visible as a result of discoloration). - After touching these moist spots with a dry hand, no moisture may be visible on it. A blotting paper or

absorbent news paper placed on the moist spots may not show any discoloration as a result of water absorption.

Comparison: Requirement according to Swiss Standard - Dry to slightly moist. - Single failing parts permitted. No dropping water on the dry part of the tunnel surface permitted. Requirements regarding substrate The substrate consists of shotcrete applied the following specifications:

1. Roughness: 4-16 mm In accordance with ZTV-SIB Sandfill method, measured at 250 mm drill cores

2. Evenness: 10 : 1

Remark concerning the degree of evenness:

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Due to the specified “almost creaseless” and surface close application of 3 mm membranes we recommend: 10 : 1 for PVC membranes and 12-15 : 1 for FPO membranes. The requirements regarding evenness were met with shotcrete with the following mix designs: Wet sprayed concrete: B 25/15 Cement content: 450 kg/m3, grain size: 0-4 mm spraying output: approx. 6-8 m3/h onto a layer of wet sprayed concrete: B 35/25, cement content: 425 kg/m3, grain size: 0-8 mm, spraying output: approx.10-14 m3/h. For purposes of testing the roughness, a sample of shotcrete was applied onto a 40 x 40 cm precast concrete slab and approved by the waterproofing subcontractor. When required, the sample has been compared visually with the applied shotcrete. Compartmental sealing off "Dammring" At the interfaces between the different waterproofing systems it was necessary to install a tight sealing ring system - a "Dammring" - between rock and waterproofing membrane. For that, 4 sealing strips have been bonded with epoxy adhesive onto the shotcrete substrate at about 2 metres intervals. The waterproofing membrane has been welded onto these strips; the membrane was fitted with injection sleeves and subsequently systematically injected. In order to exclude infiltration around the seal in the surrounding ground, 1 metre deep holes have systematically been drilled radially and subsequently injected. Fleece / Drainage mats Our experience as well as corresponding trials performed for instance in the course of the evaluation procedure for the waterproofing systems for the longest railway tunnel in the world being at present under construction, have shown that the types of fleece used up till now are not appropriate for drained, non-pressure-containing waterproofing systems. Such types of fleece are pressed together and get clogged up sooner or later. As a consequence water pressure is partially building up, stressing the waterproofing system which is not designed for containing water pressure. Damages are therefore inevitable. This is the reason why the following materials were used: - In zones with drained, non-pressure-containing waterproofing system:

Enkamat drainage mats of approx. 8 mm thickness - In ground water zones with water pressure-containing waterproofing system: (Submarine method)

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Geotextile fleece, 1000 gr / m2 (2 x 500 gr)

Waterproofing system non water pressure-containing

Cross section integral waterproofing, non water pressure-containing, in the TBM excavation section

The build-up of the waterproofing system comprises an 8 mm thick Enkamat- drainage layer fixed onto the shotcrete and a 3 mm thick polymer waterproofing membrane Sikaplan 30 PECO, installed all around. The drainage consists of a 250 millimetre drainage pipe embedded in gravel and covered with a knobbed, 1,5 m wide drainage mat. In the invert zone a 3 mm protective membrane is welded onto the waterproofing membrane. The waterproofing of the tunnel vault consists of a single, 3 mm thick membrane. Protective membranes are applied only in zones with steel reinforcements. In Switzerland tunnels are in principle not reinforced. The intermediate tunnel roof slab joint in the Uetliberg tunnel is an exception. This joint zone is reinforced for structural reasons and therefore covered with a 1.5 metre wide protective membrane. For purposes of compartmental sealing off, type Sika AR 40/6 PECO inject waterbars have been welded all around onto the waterproofing membrane., at 75 metres intervals in the middle of a block, in order to limit the field needing injection in case of possible leakage. The waterbars are made from the same material as the waterproofing membranes and are therefore compatible and perfectly weldable. In zones without water pressure no injection tubes were installed. I case of the need for injections, holes will therefore have to be drilled through the inner concrete lining. Remark: We recommend compartmental sealing off by means of waterbars also for waterproofing systems not containing water pressure. Taking this measure prevents uncontrolled spreading of leaking water and makes repair work in possible leakage zones much easier. Injections must however be carried out with due caution in order to avoid clogging of the drainage system.

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Sika-Waterbar AR 40/6 inject • Resin Injections into waterbar injection-channel • Cement Injections through Sika injection inlet-element Experience shows that surface waterbars in the tunnel vault crest zone, even if installed professionally, are hardly ever properly embedded in the concrete if not additional measures are taken. Injection sleeves are therefore installed in the tunnel vault crest zone, allowing on the one hand the entrapped air to escape, and on the other hand to inject cement suspensions. These injections were carried out systematically, unlike the injection of the waterbars done only if and when required, in addition to the tunnel vault crest injections.

Invert zone waterproofing: 3mm Sikaplan waterproofing membrane with protective membrane

Tunnel vault waterproofing: 3mm Sikaplan waterproofing membrane, protective membrane only in the block joint areas

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Joint between tunnel invert and vault

The joint between invert and vault has been sealed off by means of two single-fin waterbars type Sika AR 10/1 PECO which have been welded to the waterbar sealing rings and have been systematically injected. The main reason for this measure is eliminating the risk of damaging the membrane around edges in the invert/vault joint zone. Such damages would inevitably occur due to the effect of the pressure of the inner lining concrete, varying in function of the compressive strength of substrate and drainage material. Waterproofing system, containing water pressure

Cross section Normal profile, containing water pressure

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For the invert, a two-layer injectable waterproofing system designed for a maximum water pressure of 5 bar is used. The build-up comprises 2 x 500 gr. fleece protective layer fastened onto the shotcrete substrate and the membrane, an outer 3 mm Sikaplan-PECO 30 waterproofing membrane and a 3 mm Sikaplan-30 PECO DIA knobbed membrane welded onto it.

Double layer sealing system, Injection connections and pipes in invert area

For the tunnel vault, the thickness of the knobbed membrane is reduced from 3 to 2 mm, except in the zones of the transversal galleries and the reinforced concrete zones, where also 3 mm thick membranes are used.

in waste air shaft With protection layer, Sikaplan Protect 2mm

Saeling detail with injecable waterbar and connection flange and injection hoses

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Groundwater relief element and „Rückfallebene“ ("second defence line", injectable and drainable, connected to the drainage system)

Injection sleeves for the grouting of the space between the two waterproofing membranes, are fitted onto the inner membrane and connected to injection tubes running through the tunnel lining concrete. These tubes end up in a control box remaining always accessible. This allows checking of the waterproofing system at any time. Leaking water can this way either be evacuated into the tunnel drainage system (Rückfallebene = second defence line) or the leaking zone can be sealed by means of injections. Water seepage during construction phase calls for additional measures. Ground water relief elements are necessary for evacuation of the water. The tubes of the relief elements must be tightly sealed at the time of completion of the project. These relief elements are situated in the duct channel and therefore always accessible. In our case they will not be covered with concrete but will remain accessible for monitoring purposes. The relief elements have been fitted with pressure gauges for checking the waterpressure.

Groundwater relief element and „Rückfallebene“ Block joint seal The joint between the tunnel invert and vault has been carried out according to the already described sealing off system by means of single-fin waterbars and systematic injections. The block joints have been carried out with Sika AR 60/6 Inject special waterbars. The waterbars have a smooth, 25 cm wide middle section without fins, serving as support for the shuttering and protecting the membrane from being damaged. In the crown of the vault, the waterbar is fitted with injection sleeves for grouting with cement suspension.

Waterbar Sika AR 60/6 inject and shuttering

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Transverse connection galleries Transverse galleries and niches are also waterproofed and sealed off by waterbars. Membrane installation method Tunnel professionals have known for years that laying membranes closely to the substrate and fastening them as carefully as possible is determining for the successful performance of the waterproofing system. This is the reason why for several years now membrane installation methods aiming in that direction are being developed. SikaBau has developed and continuously improved such a method which is now being used in the Uetliberg tunnels. The method consists of a laying installation allowing the laying of pre-assembled 4.40 m wide membrane sheets by pressing them with mobile rolls onto the substrate and fastening them by means of the Velcro® system. Weak points resulting from manual welding are thus avoided and creasing is practically eliminated.

Velcro laying installation SikaBau AG Costs The costs for the Uetliberg tunnels run up to 1'120 million CHF.All waterproofing measures ad up to 30 million CHF. So the total costs for the waterproofing represent 2.7% of the costs for the whole project.

Conclusion Not only the fact that ever more tunnels are built in ground water zones and bad experience of project owners with recently built tunnels, most of them leaking and causing enormous repair and maintenance costs, but also the generally higher quality standards call for innovative solutions for waterproofing work.

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Thank God, the still often heard quality requirement : „Raining outside, raining inside“ makes little by little way for higher quality requirements. For the Uetliberg tunnels, project owner, project designer, main contractor and waterproofing sub-contractor have co-operated in designing a waterproofing concept representing the middle course between the desirable, the technically and economically feasible and the practical. The solution is the result of years of experience, development work and innovative laying technology. The costs for the waterproofing, representing approximately 2.7% of the total project costs, are in spite of that very modest. 1) Author: Roland Förstler, Sika Schweiz AG Tunneling Mining, e-mail: foerstler.roland@ch.sika.com Tel: +41 55 640 41 67/ Fax +41 55 650 26 65/ Bellikonerstrasse 218/ CH-8967 Widen