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| PERI: Crosscut between the new and old tunnel tubes  Alpine BeMo Tunnelling GmbH is currently realizing the second tube of the Pfänder Tunnel. The new main tunnel has been excavated with a tunnel boring machine whilst tubbings have been installed as the inner tunnel lining. As part of concreting operations for the inner shell, a crosscut FQ 1 for vehicle use is being constructed at present. Due to the small length of the tunnel, an economical formwork solution was required. The tunnel formwork carriage designed and supplied by PERI consisted to a large extent of rentable VARIOKIT system components and thus fulfilled the prerequisite of maximum cost effectiveness.Situated in the Austrian Vorarlberg region, the east tube of the Pfänder Tunnel was commissioned around 30 years ago but is no longer able to cope with the substantial increase in the volume of traffic. As a result, a parallel positioned, two-lane tunnel tube is currently being constructed. Over a period of 14 months, a TBM with a diameter of almost 12 m drilled 6,600 metres through the Pfänder mountains to form the main tunnel. The rock surface was then lined with precast lining segments. In the event of any fire breaking out, the planning includes 31 connecting passageways between the old and new tunnel tubes for evacuation purposes. At the moment, the most important of these connections is being constructed – the 43.10 m long crosscut FQ 1 which is suitable for traffic. Due to the small length of this tube, the main focus for the contractor – Alpine BeMo Tunnelling GmbH (ABT) – was the cost effectiveness of the formwork solution. All other crosscuts with smaller cross sections will be subsequently have shotcreted inner shells. Within a very short space of time, PERI created a tailored formwork solution on the basis of the VARIOKIT engineering construction kit. The majority of the components for the project-related formwork carriage originated from the rentable standard product programme. In addition, there were a few special parts as well as the expendable material including the formlining. The tunnel formwork used is therefore not only extremely cost-effective; a big advantage for the contractor was also the short-term deliverability. A total of seven round-shaped wall formwork elements were prefabricated in the PERI assembly hall and supplied just in time to the construction site. This minimized the assembly time on the site: after only 1.5 weeks of on-site assembly, the construction team could begin work on the first of altogether seven concreting segments. The standard length of these tunnel segments was 5.90 m and, after a short period of introduction, a 3 day cycle could be achieved for these sections. Construction of the two last segments, 3.35 m long in each case, required two days respectively. Due to the small length of the tunnel, PERI designed a mechanical solution for the formwork carriage operations. Generously-sized working levels served the simple operability which – apart from high degree of safety – was given top priority. With easy and simple spindling for shuttering and striking, the formwork carriage was moved each time to the next concreting section by means of flanged wheels on crane rails. In spite of its filigree construction, the formwork carriage provided high dimensional stability which resulted in excellent concrete finishes. For planning purposes, the PERI team required only three weeks to supply the client with the drawings featuring all necessary sections and details as well as corresponding general arrangement and assembly plans for the formwork construction. After the delivery of the pre assembled elements, the formwork carriage unit was completely assembled by PERI on site and handed over to the construction team ready to use. PERI also developed the formwork solution for the forming of the FQ 1 connection to the new main tubes. This construction, too, consists of system components such as SLS heavy-duty spindles, RCS rails, GT 24 formwork girders and SRU walers. It serves to construct the intersection area of the two tubes. write your comments about the article :: © 2010 Construction News :: home page |