RMD Kwikform pulls out all the stops to win a contract from Bouygues Travaux Publics and Dunne Building & Civil Engineering for the Tyne Tunnel, creating a unique concept for a 21 metre long, 60 tonne falsework traveller system - in just 7 days.
For formwork and falsework specialist RMD Kwikform, given 7 days to go back to the drawing board, following an unsuccessful bid for an important contract on the Tyne Tunnel, led to the conception of the company’s most innovative travelling tunnel soffit support system to date.
Having secured the deal through Concessionaire TT2’s main Design and Build Contractor Bouygues Travaux Publics at the final hour, engineers teamed up with North tunnel section subcontractor, Dunne Building & Civil Engineering, combining expertise to successfully utilise the unique traveller system.
Travelling on the equivalent of train tracks, the RMD Kwikform traveller used a combination of specially designed and standard equipment to create a solid yet flexible structure, capable of snaking up an incline of 6%. Withstanding loads of up to 750 tonnes the traveller was capable of supporting up to 300 cubic metres of concrete poured over 173 square metres.
As of October 26th 2009, the 21m long traveller system has been used by Dunne Civil Engineering to successfully cast six of the of nine, 1200mm thick roof slabs that make up the roof of the tunnel’s North section for the Tyne Tunnel operator, TT2 who, together with Project Promoter the Tyne and Wear Integrated Transport Authority (TWITA), funded £260m project.
For RMD Kwikform Engineering Director, Ian Fryer who led the four strong engineering design team for the project, overcoming the challenges faced at both the design and utilisation stages of the project were particularly rewarding. Ian: “When you are challenged to go back to the drawing board on a project of this scale and importance, it tests all of your engineering knowledge and capabilities.
“The challenge was to deliver a whole-slab-area travelling formwork system with 2 metre height variation which could be operated without the site staff working at height. The traveller also needed to give the users the flexibility to snake the equipment up an incline of 6%, travelling on rails whilst casting a slab that was up to 8.5 metres off the ground, at the bottom of a 25 metre deep excavation full of large ground shoring props.
“Once we had overcome the design element and been awarded the contract by Bouygues Travaux Publics, we entered the phase of taking the proposal design to the end solution. At this time, because the works for the North contract were subcontracted to Dunne Civil Engineering, we had to deal with a new construction team to demonstrate how the system would work.
“At this stage Dunne’s were able to assist the design team with suggested amends to the design in order for the system to best meet the needs of the site team. The very tight programme schedule also placed further challenges on the delivery and erection of equipment, which physically required assembling and commissioning 60 tonnes of system and special components at the base of what is effectively a large hole.
“As part of the intensive design and detailing phase that followed, the first thing the team concentrated on was the calculations, detailing, procurement and fabrication of the special items of equipment needed for the project. Shortly followed by production of the general arrangement drawings required for assembly and the detailed instructions for use of the machine.
Procurement of the special equipment, (which included the hydraulic leg components that were central to the function of the traveller), ultimately determined whether the system could be assembled and operated within the time frame required.”
Having developed an assembly sequence in collaboration with Dunne’s for the traveller, RMD Kwikform provided three customer service team members to assist with the erection of the traveller which as a part of the design required the support legs to always be perpendicular to the slope of the soffit.
Commenting on the soffit pours and the traveller system Philip Beausang, Project engineer for Dunne Building & Civil Engineering said: “Whereas the base slab rises at a continuous 6% incline, the height of the tunnel changes multiple times throughout its length, so at some time the soffit slopes by up to 12%.
“With all the challenges we faced on the project, it was actually the very first pour that had the most severe soffit slope. We were therefore tasked with setting up a unique never-before-used system in the hardest possible arrangement!
“We had just three weeks to complete the assembly and commissioning phase of the project and were pleased to have the support of three of RMD Kwikform’s customer service team for this phase and for subsequent coarse level adjustments.
“Although we had a challenging start to the project, by working through the early stages with RMD Kwikform, our team were able to carry out all of the required operations without the need for further assistance. As we have grown in confidence with the system, we have been able to benefit from the speed and simplicity the traveller offers us and have been impressed with its performance.”
Unlike previous travellers designed by RMD Kwikform, which incorporated structural steel work at the soffit level, the RMD Kwikform engineering team recognised the opportunity to adapt its R700 truss girder panels for use on this project. By adapting the R700 girders with specially fabricated cantilever frames at the ends, the units were used to span across the tunnel whilst still maintaining sufficient headroom beneath to accommodate site traffic, such as concrete mixers and scissor lifts.
Ian: “In using the R700 girders this had the effect of simplifying and speeding up detailing, whilst increasing the proportion of standard hire
