2005 - Putzmeister

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18PM 3652 GBTunnel ConstructionSecuring the Sedrun section of the NEATwith wet spray shotcreteOn the construction sections of the 57 kmGotthard Base Tunnel, numerous concretespray systems are being used all day, everyday by the Sika-Putzmeister alliance. Onthe middle section of the Sedrun project,the tunnel builders are working underextremely difficult conditions with fourSika-Putzmeister type 500 wet spray units.The Gotthard Base Tunnel is at the heart ofthe new Transalpine Railway (NEAT),which links rail passengers and rail freightthrough Switzerland to European highspeed rail networks. The track is beingbuilt as a flat railway underneath the mainridge of the Swiss Alps, in contrast to theold Gotthard tunnel which was situated atan altitude of 1,100 metres. At 550 m, thenew apex is just 130 m higher than thecentral station in Zurich. This satisfies animportant pre-requisite, meaning that asfrom the year 2015 – according to planning– trains travelling at up to 250 km/h (orgoods trains travelling up to 160 km/h) canpass through Switzerland on the northsouthaxis. The two tunnels will run parallelto each other separated by 40 m. Thetunnels are connected by transverse tunnelsat 300 m intervals.Since the track is being laid in two singletracktunnels and to shorten the constructiontime, several lateral access gatewayswill be required, a total of 153.4 km oftunnels, cross-tunnels and shafts will needto be built to cross the Gotthard mountainrange. The tunnels have been subdividedinto the following sections: Erstfeld,Amsteg, Sedrun, Faido and Bodio. Whilstfour of these project sections are being progressedvia the north and south portals orvia lateral mid-section cross-tunnels, theSedrun tunnel section can only be reachedvia two shafts situated very close to eachother (Ø 7 and 8 m), which have been sunkup to 800 m deep. From the common shafthead, a 1,000 m long cross-tunnel with arail system and also a 450 m long horizontalventilation cross-tunnel lead to the openair. The two shafts create the connection tothe tunnel level from which the Sedrunmulti function zone excavations are beingblasted out of the rock. The two tunnelsections – each 6.2 km long – has beendriven from here in both north and southTemporaryaccommodationDiagram of the Sedrun section of theGotthard Base Tunnel(Diagram: AlpTransit Gotthard AG)Sedruntunneldirections since summer 2003. The TRAN-SCO consortium – consisting of BATI-GROUP AG (Zürich), FRUTIGER AG(Thun), BILFINGER BERGER(Mannheim) and PIZZAROTTI SPa(Parma) – is building the Sedrun section.The works contract, signed by AlpTransitGotthard AG and the TRANSCO-Sedrunconsortium in April 2002, is worth a totalof 1,165 billion Swiss francs.Huge excavations and high temperaturesundergroundThe multifunction area is a branched tunnelsystem which will enable the trains toswitch tracks once it is completed. In addition,three large longitudinal caverns andone transverse cavern are being dug out ofthe rock (with dimensions up to 180 m x17 m x 15 m). To these will be added transversetunnels and spaces in which emergencystops, evacuation zones, maintenanceworkshops and technical assistance centreswill be set up later on. At the moment thereare vast construction site installations,materials stores, a concrete mixing plant,workshops, underground water pumpingsystems, etc. in the area at the base of theshaft.The overburden of the alpine rock also hasconsequences for the water and the temperatureof the rock. In the Sedrun section, theoverburden of up to 2,500 m is comparativelydeep. At 45 °C, the temperatures hereare particularly high. The consortium hasbeen able to lower the temperature considerably,to 28 °C, by deploying hugecooling systems.Sliding arch constructions are familiar from coalmining. Due to the pressure exerted by the rock, thisprocess is also being used in the Sedrun section.(Picture: AlpTransit Gotthard AG)Access driftsNorthernportal20.9 km awayNorthern tunnelling work,approximately 2.1 kmVentilation system structure1517 above sea levelVentilation driftsDelivery machine roomSouthern portal,approximately35.8 km awaySouthern tunnelling work,approximately 4.2 kmA new way for tunnel buildingWhilst four sections of the Gotthard basetunnel are being carved out with the tunnelshield advance method, tunnelling underneathSedrun is by blasting. The standardcross section of the main tunnel takes upabout 68 m 3 . For larger formations, theexcavation can be twice as great (up to135 m 3 ). The reason for the conventionaltunnelling in Sedrun is the pressurised(”swelling“) rock type, in other words, thevoids cut from it tend to close up again ifno countermeasures are taken.It is therefore necessary to use props tokeep the void open. If, after breaking thepressurised rock face, a specified level ofdeformation is permitted, the mountain’sresistance to tunnelling work can be considerablyreduced – to keep the excavationopen.For this reason, two interlinking steelarches will be built in sections once theTunnel Construction40 41Not just both the main tunnels, but also the numerous transverse galleries and large voids are being secured with shotcrete. Our photo shows a Sika-PM 500 wet spray machineworking around the corner.42rock face has been broken (the depth of theblasting in these difficult zones is onlyapproximately 1 metre). When the rockpressure begins to take effect, the ring halvescan push into each other until maximumresistance is reached. This ”deformablesteelwork“ is known in the German coalmining industry as ”sliding arch construction“,but has never before been applied tosuch a great extent.The waste rock is transported to head ofthe shaft via the materials elevator and thentaken by platform truck to the processingplant on the outskirts of Sedrun. Once ithas been crushed and sorted, part of thestone material is taken back underground,where, at the foot of the shaft, it will beused as concrete aggregate in a speciallyerected concrete mixing plant. Truckmixers with 4 to 7 m 3 mixer drums thentransport the material to the six shotcretesystems on the Sika-Putzmeister 500 (4 x)and Aliva-500 (2 x) product lines.19PM 3652 GB
Tunnel ConstructionPractical Tip43Clogged delivery pipescan become expensive46On most construction sites which use stationaryconcrete pumps to pump overdistances or to heights, trained machineoperators are responsible for flawless operation,for maintenance works and forcleaning the pumps and delivery lines.And in general, they do a good job.Occasionally, however, Putzmeister customerservice centres are amazed by thelevel of ignorance and by the indifferenceof some machine operators and constructionmanagers. Here is a recent example.47The accommodation camp for the Sedrun tunnel builders with smashing plant for processing the tunnel waste, which is brought up from a depth of 800 m undergroundThe six shotcrete units carry are responsiblefor initially securing the stretches of tunnelwhich have just been driven using steelfibre shotcrete. Approximately 27 kg ofthese roughly 5 cm long steel fibres aremixed into every cubic metre of concrete.The shotcrete is applied in several layers,for a final thickness of 15 to 20 cm.Drainage material and sealing foils will beadded to the shotcrete shell at a later stage.The internal formwork will then be produced.This formwork generally has a wallthickness of 30 cm, but can reach a thicknessof 1.2 m due to the enormous pressuregenerated inside the mountain in theSedrun section.Each of the tunnels is watched over by a patron saint –Saint Barbara44Reliable service, rapid componentacquisition and special concrete additivesThe TRANSCO-Sedrun consortium hascommissioned a specialised, externalservicing workshop to carry out the regularmaintenance works on the shotcrete units.There is also a SIKA employee employedpermanently on the construction site, toliaise with the TRANSO-Sedrun consortium.In addition to the different shotcrete units,SIKA also supplies highly efficient concreteand shotcrete additives for the Sedrun sectionand also for further project sections ofthe Gotthard Base Tunnel. These are mostlyadditives which help to satisfy the sometimesvery specialised and demanding con-crete and shotcrete requirements for thissophisticated tunnel project. Example:additives supplied by Sika include silicafume additives, which increase the watertightnessand the durability of the shotcrete,retarders which enable the required processingtime to be adjusted, a solvent tosecure the stipulated water/cement valuesand a non-alkaline setting acceleratorwhich enables the short concrete settinglead times which are stipulated to be met.The exact mixture breakdowns for the concreteand shotcrete that is used have beentested by the client since 1996 under adetailed and stipulated pre-qualifyingprocess These breakdowns form the basisof the mixtures now used on all Gotthardtunnel construction sites.45A branch of Putzmeister AG rents out astationary BSA concrete pump, approximately140 m of ZX-delivery line, a gatevalve and a stationary MX concrete placingboom for a high-rise project within theirsales region. The machines are ideally setup for the conditions of the constructionsite by the Putzmeister service team andthe delivery line (30 m horizontal and thefirst 20 m vertical) is installed. So far, sogood. The delivery line is extended as thework progresses by the construction sitepersonnel.During the ensuing months of concreting,more and more phone calls are made by theexasperated construction management:there are constant problems when startingpumping, the concrete pump needs toomuch time to deliver the required deliveryrate, the hydraulic pressure of the machineis too high, more and more blockages areoccurring, etc.For these shabby pipes, a ”build-up of lubricating film“ for the concrete delivery is now virtually out of the question...A Putzmeister service technician comes tothe site several times and ”oversees“ ormonitors cleaning after several hours ofpumping. On the following day, no difficultieswere experienced when pumping started.For the next few days, when noPutzmeister personnel are on site when thepump is being cleaned, the relevant constructionmanager/foreman phones upagain to complain about the ”wretched concretepump“.The last few metres have finally been pumpedand the MX boom including deliveryline can be dismantled. When the pump isre-delivered to the Putzmeister branch, theresult of inspecting the pipes can be seen inthe picture above: instead of a smooth48inner wall with a build-up of lubricatingfilm, almost all the 3 metre long pipesreveal a layer of concrete residue on theinside – for a total of approximately 100metres of pipeline. By heating the pipescarefully and then treating them with a2500 bar DYNAJET high-pressure cleanerwith rotating nozzle, it was possible toremove the concrete encrustation (approximately5 mm thick) from the inside of thepipes after much time-consuming, minutework. The damage that was caused byuntrained personnel is estimated at25,000 to 30,000.4920PM 3652 GBA Sika employee is on site constantly to provide liaisonThe encrusted concrete residue can be loosenedfrom the pipe walls with the DYNAJET high-pressurecleaners21PM 3652 GB
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2005 - Putzmeister

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