Wirth Tunnel Bore Extender at Uetliberg Receives AwardWirth has been chosen as the winner of this year's TTC Award for Innovation in the Large Bore Mechanised TunnelIing Machine sector. Mr Niko Kleuters, Chairman of the Wirth Group, received the prize on 14th September, 2005 at a ceremony held during the IUT' 05 Live Fair in Hagerbach test galleries in Switzerland. Wirth received the award for its tunnel bore reamer (TBE) 500/1440 H-HST, which is being used successfully on the Uetliberg road tunnel in Switzerland - part of Zurich's southwest ring road bypass, due to enter in service in 2008. The 10.6 km bypass runs approximately 80% in tunnel and will connect the Birmensdorf bypass in the west with the Zurich-Chur motorway A3 along Lake Zurich (view map here). The backbone of the project is the 4,460 m Uetliberg twin bored tunnel, connected every 300 m by pedestrian crosscuts and every 900 m by vehicular cross passages. This highly technological machine broke through the first tube of the Uetliberg tunnel on 1st February, 2005 (read more here and view picture here). The TBE started the second tube at Uetliberg, direction Chur, on 7th June, 2005. The TBE will expand 1,850 m of the Chur-bound tube, instead of 2,800 m as was the case for the first tube towards Basel, since a drive was launched from the opposite direction to meet the project schedule. This drive is now completed. To date, approximately 480 m has been excavated in the second tube by the TBE. The Public Works Department of the Canton of Zurich is the client. Amberg Engineering is the project designer and construction manager. The contracting JV, ARGE Uetli, includes Zschokke Locher, Murer-Strabag, Prader, CSC, Alpine Mayreder, Wayss & Freytag and Zueblin. Visit www.bd.zh.ch, www.amberg.ch and www.arge-uetli.chWirth's TBE is currently the world's largest operating hard rock TBM to date, with a cutting diameter of 14.4 metres and it works as an undercutter/reamer enlarging a pilot tunnel to the full dimension. The TBE's boring head consists of a two-piece cutterhead body and six cutter arms. The boring head rotates on the interior kelly, which is braced and positioned in the pilot tunnel and in the extended tunnel cross section. The cutting rollers, which are offset both axially and radially from the tunnel axis, are mounted on radially movable slides on the cutter arms. Superposition of the slides' radial movement on the rotation of the boring head causes each cutting roller to follow a spiral path around the tunnel axis. Because the outermost cutter on each arm leads the rest, the face area assumes a stairstep profile that enables each cutter to shear away the molasse against an open surface by the undercutting principle. The advance is limited to a maximum length of 20 cm by the axial displacement of the rollers on the slides, which ranges from 60 to 80 cm. Shorter advances can be used where harder rock is encountered. Between eight and ten rotations of the boring head are required for an advance. When the six-arm head turns, the rollers are shifted from an inner to an outer boring diameter. When the nominal boring diameter has been reached, the slides are retracted radially. Then the continuously rotating head is shifted by one 20 cm advance toward the face, and boring of the next advance (renewed outward travel of the slides) can begin (view pictures of the cutterhead here). This is a unique machine in the modern tunnelling world. The entire TBE with its back-up is about 180 m long and weighs approx. 1,000 tonnes. The reaming technology was developed by Wirth in the 1970s. This technology was and is still applied in a variety of projects around the world, such as high speed rail tunnels in Spain, shafts for hydropower plants in Japan and Korea or road tunnels in Italy and Switzerland. For the first time in the tunnelling sector, the TBE combines the reaming technology with the undercutting technology. The machine offers a wide range of advantages, among which a considerable energy cost reduction. Visit www.wirth-europe.comFor the Uetliberg tunnel, project designers considered and assessed two different building methods: conventional tunnelling in sequential excavation phases, with a horseshoe profile and curved invert, and full-face tunnelling using a TBM. In the hard molasse, the TBM showed advantages against the conventional method, but was judged riskier for the soft ground material. The final decision was to use conventional means in loose ground and a TBM in the harder molasse. When the bids were opened, it appeared that one of the tenderers, the Uetli JV, submitted the proposal to operate a reamer TBM for the rock stretch. But the available machines were approximately 12 m in diameter, an insufficient dimension to meet the project requirements. However, the JV suggested an extension of the diameter with a reaming machine operated with the undercutting technique. The principle of the undercutting technique has been known for a long time and Wirth had already built these machines which worked from these principles. However, it was never implemented with a TBM. In many ways the undercutting technique is an interesting alternative, with respect to the routine principles of the mechanics of tunnelling. The Uetli JV suggested a variant which was also economically attractive, offering an ideal opportunity to the undercutting technique in combination with a TBM to test the actual suitability of the operation in practice. This test proved successful. Along with the knowledge and experience gained it was extremely valuable in view of the application of this technology in difficult conditions in the future. In this sense, the operation of the undercutting technique with the TBM at Uetliberg paves the way for the adoption of this innovative technology on other tunnel projects. The tunnel is driven downhill from west to east starting from Reppisch Valley shaft. From May 2002, a Wirth TBM drove the first of two 5 m-diameter pilot tunnels through the entire Uetliberg molasse section (read E-News Weekly 24/2002). Concurrently, this time was used to proceed with the planning and manufacturing of the cutter head of the undercutting technology. In October 2002, the TBE was ready. At Wirth's plant in Erkelenz, Germany a delegation of project team members viewed the newly designed cutterhead with imposing dimensions (view picture here). At that time, all were conscious of the tunnelling potential of the enormous 14.4 m-diameter machine. In the following months, the 550 tonnes of steel were transported to the jobsite where the TBE reaming machine was assembled on a TBM provided by the Uetli JV. Rather than a new TBM, the JV opted for a comparatively economical solution by purchasing a new cutter head only, the TBE, mounted on an existing TBM fitted for a maximum boring diameter of 12.46 m (view picture here). Compared with usual mechanised tunnelling, the TBE consumes only half the energy required per cubic metre of rock, not to mention smaller electrical outfit and lower electricity costs. After an assembly time of four months, the TBE crushed the first metres of rock on 11th April, 2003 while at the same time, the TBM started driving the second pilot bore for the future Basel-bound, north tunnel. In the following 22 months, after unavoidable teething problems as is usual at the beginning of new developments, the Uetliberg tunnelling reached a peak rate of up to 16.5 m per day. The average weekly rate reached 45-55 m. View picture here. The first pilot tunnel has holed through on 20th February, 2003.From west to east, the Uetliberg tunnel crosses two hills, Ettenberg and Uetliberg. Between them lies the Reppisch Valley, which divides the tunnel into two independent bored sections: the 710 m-long Eichholz tunnel under Ettenberg and the 3,450 m Uetliberg tunnel under the mountain of the same name. A 300 m cut-and-cover section in Reppisch Valley, where is also the ventilation station, joins the two tunnels. The Eichholz tunnel crosses the Gjuch soft ground section (210 m) and a molasse section (500 m). The Gjuch section, starting at the Wannenboden west portal, passes through a very heterogeneous and moraine complex consisting of loamy, sandy gravel. East of Reppisch Valley construction shaft in Landikon, the tunnel crosses the Uetliberg through the Diebis soft ground section (240 m), which is ground moraine covered by aquiferous slope wash (moraine material and fines). Then the tunnel cuts through a 2.8 km molasse section. The Eichholz and Uetliberg molasse sections consist of flat layers of the upper freshwater molasse, with hard banks of sandstone alternating with soft marl deposits. The highest overburden at Uetliberg reaches about 320 m. At the east end of the alignment, the tunnel traverses the Juchegg soft ground section (410 m) to reach the Gänziloo portal near Zurich south interchange at Brunau. This stretch comprises a ground moraine that starts as gravelly sand and then turns into more sandy clay.Tunnelling is finished on all soft ground sections (Gjuch, Diebis and Juchegg, 2 x 860 m in all) and the Eichholz molasse portion (2 x 500 m). Conventional methods were used in the loose ground and drill-and-blast in the Eichholz molasse. The cross section is 143-148 sq m (14.7 m wide x 12.7 m high). The molasse section under Uetliberg is 14.4 wide and 14.2 high. The Wirth TBE 500/1440 H-HST combines therefore reaming techniques, an undercutting technique and the ability to bore tunnel sections which are not round. The project is now 80% completed. Click ch/24. To read more on the TBE, click here. Visit www.uetlibergtunnel.ch and www.westumfahrung.ch 39/05. Wirth's Chairman Niko Kleuters (left) receives the Large Bore Innovation Award from Lawrence Williams, editor of Tunnelling & Trenchless Construction magazine.