DE
Work on Dresden's first accessible Elbe tunnel began in June 2019. However, this Elbe tunnel is only accessible to maintenance personnel from the client and user DREWAG Netz GmbH. In accordance with the client's design, the 240-metre-long tunnel is being constructed using reinforced concrete pipes. The reinforced concrete pipes have an outer diameter of 3.20 metres and one shaft structure on each side of the tunnel. The clear dimensions of the shaft structures are 6 metres x 10 metres x 18 metres and 5 metres x 6 metres x 18 metres respectively.
The start
Work begins with the starting pit on Pieschener Allee. It will be sunk to a depth of 22 metres using a starting shaft structure as a lowering structure. For this step, it is first necessary to replace the soil at full depth, as the existing soil does not permit a lowering process. Once the ground has been cleared by breaking up the surface and subsequent explosive ordnance investigations, work is currently underway to replace the soil using a large rotary drilling rig. The enormous starting shaft in in-situ concrete construction has a circumferential wall thickness of 1.5 metres and external dimensions of 13 metres x 9 metres.
The lowering process will be carried out entirely in (ground) water.
A 3 metre thick underwater concrete layer will then be installed as a floor slab. After this step, the structure is sufficiently dense and heavy enough to support the structure and carry out the preparations for tunnelling. On the opposite side of the Elbe, this work for the target structure will be carried out in the same way on both sides. Eiffage Infra-Vortriebstechnik can then begin the tunnelling section.
Update: 25 October 2019
Start of civil engineering and structural engineering works on structure 1
After completion of the special civil engineering, the advance excavation for structure 1 (caisson) began on 7 October 2019.
On 14 October 2019, our structural engineers were able to take over the construction site and complete the work on the clean layer, formwork, negative mould for the cutting edge structure including the installation part by 18 October 2019.
The reinforcement work is scheduled for 42nd calendar week 2019 and the first structural concrete is to be installed from 01 November 2019.
Update 25/06/2020
After working exclusively with rental technology in recent years, the Structural Engineering division has now procured its first tower crane - a Liebherr 81K1.
The machine was delivered directly to the "Elbdüker" construction site on 25 June 2020 and set up there for the first time.
The crane has a maximum reach of 48 metres and a maximum load capacity of 6 tonnes. The rear slewing radius can also be shortened if required on tight construction sites. The load capacity is fully maintained by adding additional counter ballast. Using "LoadPlus" technology, the maximum load capacity can be increased by an additional 10%, with the control electronics reducing the working speed to a minimum to prevent swinging movements. The slewing gear is equipped with an automatic swing-out function. All load and machine statuses can be read by the crane operator on the radio remote control display.
Approval for the use of personnel lifting equipment (e.g. crane basket) is also available. The concrete counterweights have been specially branded with the EIFFAGE company logo for an effective advertising presence. This makes the machine ideal for use on our engineering construction sites. The crane will be used to complete the target shaft at the Elbe culvert and to construct the neighbouring slide gate structure. The machine will also be used for the complete outfitting work.
Elbe culvert goes into operation
On 11 December 2020, Dresdner Stadtwerke DREWAG was able to put the new district heating pipeline with a total length of 297 m in the dimensions DN 15 - DN 500 into operation.
On 20 July 2020, Eiffage-Infra Vortriebstechnik GmbH started tunnelling in the starting shaft of the Elbe culvert. After just 6 weeks, the machine arrived in the target shaft in exactly the planned position. The tunnel boring machine was then removed within a very short time, all control, transport and feed lines were removed from the tunnel, temporary installations were dismantled and the construction site equipment for the tunnelling technology was removed to make way for the subsequent expansion of the tunnel and shafts.
Just three months after the tunnel boring machine had completed its work and could be lifted out of the target shaft, the entire district heating system - in detail, 714 welded seams in the dimensions DN 15 - DN 500 were created here - was handed over to DREWAG and put into operation by them.
The first milestone was already reached in October 2020: the Elbe culvert was integrated into the existing network on the right bank of the Elbe with the so-called Armaturenbauwerk 3 on 16 October 2020. This date was absolutely necessary before the overall commissioning, as integration would not have been possible in the colder months due to the heat demand in the network. The existing district heating route in the Elbe cycle path on Neustädter Ufer had to be taken out of operation, cooled down and drained before the flow and return could be separated and fed into the structure and then out again.
While the valve structure 3 was being built, equipped and integrated, the tunnelling and equipping work took place in parallel.
Equipping the tunnel with district heating pipes initially began with the installation of the steel structure on which the district heating pipe was to be mounted. This had to be carried by hand into the 241 metre long tunnel and installed there. At the same time, a temporary walkway and assembly route made of wooden planks was installed - also by hand - and the installation of the district heating pipes began from the starting shaft. 6 metre long media pipes were lifted into the shaft in a 2-shift operation, aligned, welded, X-rayed, released and pulled 6 metres further into the tunnel as a string, the supply and return pipes simultaneously.
Once the pipes had reached their final length and position, the roller bearings installed for pulling in had to be replaced with the slide bearings intended for operation. The pipe strings were lifted using hydraulic presses and the bearings replaced.
While the pipes coming from the tunnel were being connected to those in the valve structure, the insulation work in the tunnel began. The requirement was that all pipes had to be fitted with insulation as contact protection when they were commissioned, as the media temperatures in the pipe strings are between 60 and 130 °C.
The corona pandemic further exacerbated the already difficult logistics and tight schedule, with the sometimes considerable deployment of personnel in a very confined space.
Nevertheless, together with our client and our partners and suppliers, we managed to meet this important deadline in good time before the winter and thus secure the heat supply for many new DREWAG customers on the right bank of the Elbe.
Over the next few weeks, the ventilation, electrical and control installations, some additional steel construction work, the construction of the structural ceilings of the start and finish shafts, the dismantling of the flood protection walls, the restoration of the surfaces and various smaller ancillary services will now take place.
We would like to thank all our colleagues working on the construction site, the employees of the subcontractors and suppliers and everyone else involved for their dedication, great commitment and prudent behaviour, which made this huge achievement possible in the first place.
We would also like to thank our client, its subcontractors for quality assurance and the operator, site management and site supervision for their constructive co-operation and the pursuit of the common deadline targets on the construction site.
Press article Drewag Netz:
https://www.drewag.de/wps/portal/drewag/cms/menu_main/geschaeftskunden/die-drewag/presse/pressearchiv [11.12.2021]
