Construction work

Description

The Kvitsøy tunnel and middle section of the Boknafjord tunnel, contract — E02. The contract comprises drill and blast tunneling and securing of the tunnel, as well as road construction and all internal works in the tunnel excluding electro installations. Also included in the contract are open air road and bridge works, concrete works and vertical shafts for ventilation. In addition, stone deposits will be established and secured in the sea. E02 – The Kvitsøy tunnel and middle section of the Boknafjord tunnel, 2 ventilation shafts and 2 Km of open air county road, local roads and five bridges. The Boknafjord tunnel is being built with 2 carriageways with cross section T10.5. Each carriageway has 2 lanes and elevated side area (verge). The Kvitsøy tunnel is built with one carriageway with cross section T10.5. The crossing between these 2 tunnels is designed as a rock fly-over with 2 roundabouts. The ramps in the crossing are designed with extra width so that the crossing can be used when switching traffic over in the opposite carriageway when closing of one carriageway and the deviation of 2-way traffic in the opposite carriageway. The Boknafjord tunnel will be clad throughout with concrete elements in both walls and ceiling. The Kvitsøy tunnel will have concrete elements in walls and arches of shotcrete in the ceiling. The tunnels are longitudinally ventilated with hanging pulse fans. These are primarily located near the technical buildings c/c 1 500 m. Two ventilation shafts will be built, each with a diameter of 10 m. The shafts will each be approx. 250 m long and worked with shaft sinking from the open air vertically down to the rock hall for the shaft fans. These rock halls are connected to the main carriageways through individual shafts for air intake and air emission. The sink shafts will be sealed by pregrouting. Technical buildings will be established every third breakdown lay-by. This provides a distance of approx. 1 500 m between the structures. There will be separate electrical installations, with their own technical buildings for each carriageway. The buildings will be established in their own niches in the tunnel. The buildings contain high voltage, low voltage, emergency power, battery and tele/radio rooms. The tunnel will have comprehensive fire extinguishing water pipelines with associated pressure reduction systems. The tunnel is equipped with separate collections of washing water from extinguishers in the roadway that connect to oil separators and individual sedimentation basins and intake pools as a joint solution for both tunnel carriageways. The water is pumped up in steps with approximately 80 m elevation height. The drainage basins have an overcapacity for leaking water as preparedness for unforeseen events. The water pumps up into the open air through a pump pipeline in the Kvitsøy tunnel. At Kvitsøy, a 2.0 km two lane open air road will be built from Krossøy to crossing the existing County Road 551. A round-about, bus stop, rest area, parking space and technical installations will be built at the tunnel mouth. In addition, a new access road will be built in the current route to Krågøy, a total of approx. 1,5 km. Also approx. 1.0 km of other access roads, tractor roads and footpath and bicycle roads will be built. At Kvitsøy, a portal structure shall be for the Kvitsøy tunnel, as well as a service building for the public transport terminal, inlet and outlet structure for the ventilation shafts and 4 cast on site bridges with a width of 11 m. The bridges have the following lengths: — bridge over Leiasundet, 3 spans with a total length of 77 m, — bridge at Skjermen, a span of 20 m, — bridge at Kjørkjesundet I, a span of 16 m, — bridge at Kjørkjesundet II, a span of 16 m, — a narrow bridge at Vadvika with a span of 10 m. There is much uncertainty regarding the geology of the area. There are many zones registered with low, in places extremely low (<3 000 m/2) seismic speeds. Some of these zones are up to 10 of metres wide, and some of the assumed bad zones have not been investigated with drilling. A zone with particularly poor rock mass quality, and where adverse permeability and tension conditions result in water-borne cracks with high water pressure, could cause major problems for the tunnelling, rock support and grouting of the tunnel. Two sea filling will be established where the most stone from the tunnel will be placed. Furthermore, a quantity of tunnel mass will be freighted to other disposal sites by boat/barge.