There’s a name that keeps coming up, that of a go-to practical and resourceful Icelandic engineer and craftsman who has won the praise of many and is experienced with tunnels. He came up with fresh concepts to use on the project that gathered innovative ideas and systems to help construct insitu concrete portals in exposed, harsh, and cold conditions and then developed an efficient manufacturing-style approach to installation of water and frost proof (WFP) lining in the tunnels.

‘Helgi’, is all that needs to be said, but his full name is Helgi Valur Einarsson.

For construction of the concrete portals he came up with a system like a port-style straddle crane to move assembled arches of steel reinforcement and shutters. The formwork for casting the sections was design and produced in Prague and supplied to Iceland by Metrostav.

In the tunnel, a multi-platform gantry was created to have numerous operations underway consecutively for measurement and then installation of the WFP positioning bolts to achieve the finished profile for the lining, later to be shotcreted, despite the varied cross-section of the drill and blast excavated tunnels.

During the project, he helped to establish and co-owns VK Contractors, which worked under a subcontract for the Metrostav-Hafell joint venture contractor. Other co-owners are Johann Gunnar Stefansson and Skarphedinn Omarsson.

In the portal and open-cut works, VK Contractors was able to speed up the work cycles and increase both efficiency and productivity compared to the initial approach, resulting in much-needed cost and time savings, benefiting the construction programme.

Concrete Portals
A total of 450m of concrete portals were constructed insitu for Hedinsfjordur Tunnel project – half for each of the two tunnels, Olafsfjordur (‘Olafs’) Tunnel and Siglufjordur (‘Siglu’) Tunnel, that comprise the new road link. Olafs has portals of 150m and 75m lengths, respectively, while those at either end of Siglu are 125m and 100m.

In each case, a single tunnel has a total of 225m of concrete portals to help keep access open especially in the extremely heavy snows in this northern coastal part of Iceland, which is not too far from the Arctic Circle.

Originally, the portals were to be constructed traditionally by building the steel reinforcement into the formwork and using a number of shutter sections lifted by mobile crane. However, bad weather was interfering with the process, such as ICE build-up and snow entering the formwork, and scaffolding was needed every time for assembly. Reinforcement placed against formwork also caused extra wear and tear.

Helgi and his team came up with a new approach of concurrent activities, leaving curing time the prime time constraint. The system allowed the portals to be constructed insitu in 12m long sections, joined by a specially-designed membrane. Each 12m section took up to three days to construct. The total volume of concrete used for their construction was 5007m3 and the tonnage of steel reinforcement was 520 tonne.

Portal construction begins with preparation of the reinforced concrete foundations strips while, not far away, a specially-built, oval-shaped long multiplatform gantry is used as support for assembling of the steel reinforcement into arches matching the tunnel geometry. The gantry, running on wheels, then transports the reinforcement to the casting site where it is lifted by a horseshoe-shaped gantry crane and placed onto the awaiting full-size, inner formwork shell.

The crane then lifts the complete outer formwork in its entirety and places it on top of the reinforcement. Following bolting and sealing, the shuttered rebar is ready for concreting. Meanwhile, the multi-platform gantry is being used to begin assembling the next arch of reinforcement.

After the outer formwork is struck it is lifted by the crane, washed down and oiled, and then brought back to protectively cover the thick canvas sheets that have been placed meantime on the hardening concrete to limit heat loss. Later, the inner formwork is struck and lowered for cleaning and oiling before being put into a new position for construction of the next section of the portal – and, still having some heat from the curing concrete, there were few if any problems with snow and ice.

Shorter time and simpler processes meant fewer man and machine-hours, less risk of weather interference and better durability of equipment, and so overall better use of resources. The smooth, multi-activity operation became known as the NSH system – Non-Stop Helgi.

WFP Lining
Following the success with the manufacturing approach to concrete portal construction, the team became involved in the challenge of the WFP lining – how to efficiently and rapidly get the required length of holding bolts in the correct positions in each and every location in the tunnels, for nothing was standard.

Metrostav surveyors used SetOut software from Leica for setting out the bolt positions. This is based on surveying the cross-sections of the excavated profile and recording the data by chainage. Then, knowing the finished profile sought, software can calculate the necessary lengths of bolts for each position.

The challenge, then, was two-fold – accurately drilling at the necessary bolt positions to the required lengths, and organising a system to ensure the right bolt was where it was needed to hand as the installation process moved along the tunnel. Again, a multi-platform gantry system would play a role.

However, due to specialist, and expensive, equipment for bolt positioning and drilling not being available from Norway, an alternative – and successful – solution was elected: to carefully use the Sandvik Axera drill rig. About 46,000 bolts were installed, each 16mm in diameter. The only problem, especially during the starting period, was consumption of special drill bits, because the small diameter is not so commonly produced or used.

Then, the WFP foam lining, supplied by Skumtech of Norway, would be prepared for placement. To match the open deck transport available, the maximum length of the 2.7m wide sheets was 11.4m. The system requires a 300mm overlap in all directions – the key to prevent cold air getting into the void that is left deliberately between the lining and the excavated walls for groundwater drip space. Where there are spots of slightly more, concentrated flow, extra protection such as stainless steel sheets or GSE membrane is used to stop the WFP foam being locally weakened and ruined.

Under the brand name of Sleipnir, VK is exploring a patent for the system used for the WFP installation at Hedinsfjordur. VK anticipates it could also be useful in tunnel repair work.

Olafsfjordur Tunnel, at the south east end at Olafsfjordur town, where steel reinforcement was being assembled at the end of 2009 using a multi-platform gantry arrangement on a flat wagon to help with insitu concrete portal construction The horseshoe-shaped gantry crane running on tracks was used to lift reinforcement into place for the next stage of portal construction Final preparations are made before the horseshoe-shaped gantry crane transports the outer formwork into position for the last stage of insitu concreting works at the portal. Plastics tubes protrude up from the formwork to receive the pumped concrete Portal construction at Olafsfjordur in its final stages in February 2010, with the outer formwork removed while the inner formwork remains in place A new survey, calculation and organisational system was developed to speedily undertake installation of each individually-sized WFP positioning bolt at Hedinsfjordur