PRESENTED BY:-VIKAS MATWANID :- 130562CE:- year

CONTENTS• Introduction• Component• Description• Design condition• Construction• Project cost• Advantages

INTRODUCTION :-• The Busan – Geoje Fixed Link project is highly ambitious and

challenging infrastructure scheme to cut down journey time between korea’s south coast city of Busan and the island of Geoje. With the help of this project they manage to develop Geoje as tourist spot and save US $300 million by solving traffic related issues with the help of this project. The link consist mainly three parts which are :

8.2 km long link, which includes immersed Tunnel of 48m depth A three-pylon cable-stayed bridge Approach bridges with cable-stayed and road and rock tunnels on

islands

Project components Total length : 8.2km Lot 1 bridge : 1.65 km (1.03 mi)

Between Geoje and Jeo islands, a 1.65 km (1.03 mi) bridge includes a three-pylon cable-stay bridge. This bridge has two mainspans of 230 meters (750 ft) with side spans of 106 meters (348 ft). The pylons are 102 meters (335 ft) tall and there is 36 meters (118 ft) of clearance underneath the bridge.

Lot 2 bridge : 1.87 km (1.16 mi)

between Jungjuk and Jeo islands includes a cable-stayed bridge with a 475 m (1,558 ft) main span and 220 m (720 ft) side spans. This bridge provides 52 meters (171 ft) of navigational clearance and has two 156 m (512 ft) diamond-shaped pylons.

Lot 3 Immersed tube tunnel : 3.2km

The total length of the immersed tunnel is 4 km with two 170 metre long cut and cover sections at both ends.

Bird’s eye view of the project :-

DESCRIPTION :-Tunnel :-

• The tunnel elements on the Busan-Geoje link are large with 10 m high and an external width of 26.5m incorporates two lanes of traffic in each direction and a central services/escape tunnel. The 3.24km length of the tunnel comprises 18 elements that are 180m long.

• Each element was casted in 8 segments in the Anjeong precasting yard. This can accommodate five 180m long tunnel elements at a time.

• Each segment was casted in a continuous 24 hour operation. There were twin batching plants on site.

“We don’t want cracks so each segment is cast as one section,” says Fraser. “Also we don’t want early age cracking so thermo sensors are cast in and the heat development is monitored. We don’t use steam curing as such but steam is used to heat the external environment. Concrete generates heat so we need to keep the immediate environment warm.”

Keeping the exterior surface of the concrete warm reduces the thermal gradient across the segment, helping to limit the risk of early age thermal cracking.

The joints between the segments have two waterstops.1) The first is an injectable waterstop – a rubber seal stop with the facility to inject

epoxy resin which can make its way into small flaws or depressions in the concrete.

2) The second is an omega joint, which is a rubber and nylon membrane that arches over the joint, clamped to the tunnel element either side of the joint, able to accommodate movement caused by temperature changes, shrinkage, creep and earthquakes.

Casting yard

Bridge :-

• There are five pylons in total for the two cable stayed bridges which were built in deep sea conditions.

• Caisson foundations have been used for the piers and pylons as they eliminate the need for water excluding temporary works.

• The caissons are 33m high precast concrete cellular structures.

• The caisson foundations were fabricated at a casting yard on the mainland.

• The heaviest weighs 9,600t but the natural buoyancy of the open-celled structures was utilised when they were taken out to sea. By floating them, the weight could be shared between the water and the crane so a smaller 3,000t floating crane could be used.

Erection of pylon

Contd….

• The main pylons are up to 156m tall and are cast in-situ.

• From their caissons, two legs splay outwards until they were level with the road deck, at which point they inclined towards each other.

• The lower sections of the pylons are filled with rock ballast up to a height of

16m to protect against ship impact.

• The pylons were made from in-situ concrete distributed by a 180m3 capacity floating concrete batching plant. They were constructed in 4m high lifts using climbing formwork and concrete pumps.

• All five pylons were scheduled for completion by July 2009.

• The bridge deck consists of a steel framework which supports a concrete slab.

Contd….

• Sections of steelwork were fabricated off site in a casting yard and brought to

the yard where they were welded together before the 300mm-thick concrete

deck was casted.

• The cable-stayed deck sections were erected in a balanced cantilever

sequence. The sections were taken out to site, lifted into place, starting at the

pylon and working outwards, and the cables were connected.

• Both sides of the pylon were placed consecutively to balance the loads.

DESIGN CONDITIONS :- Hydraulic pressure :-

• The deepest foundation point of the tunnel is 47m below mean sea level.

• The water pressure imposes a significant load on the tunnel elements, in particular in the transverse direction.

• A number of other effects add to the water pressure on the tunnel. The total characteristic pressure can reach an equivalent of 58m water pressure for certain conditions.

• An increase in the mean sea level of 0.4m has been included due to the global warming.

Waves and current :-• Most waves at the project area are generated by winds including tropical storms

and typhoons. Waves generated by distant storms can also reach the tunnel alignment from southerly directions:

• A number of typhoon pass through the project area every year.

• The deep water wave height generated by typhoon and swell waves can reach 9.2m for a 10,000 year return period.

• Result from the numerical wave modelling show that the significant wave height is about 0.4 m and 0.8m at the most exposed location along the tunnel alignment.

• Tidal range varies between 0.8m and 1.6m.

• The maximum near surface current spring tide is about 0.8m/sec, reducing with depth to 0.6m/sec at near bottom.

Earthquake :-• The Busan metropolitan area is classified as a seismic zone-I based on

the result of seismic hazard analysis as specified in the Korean Standard Specification of Highway Bridges.

• Therefore, in this area the corresponding seismic zone coefficient for a 500 year return period is as---

Seismic Zone I

Zone Coefficient 0.11

• The risk coefficients representing the ratio of effective peak ground are—

Acceleration coefficient (A) = Seismic Zone Coefficient Risk Coefficient

Ship impact :-• The Southern coastline of Korea has a large volume of sea going

traffic including containerships, gas and oil tankers.

• Militarily it is an important and strategic area.

• Overall design of the Busan-Geoje Fixed Link Project considered loadings from impact and sinking of a 50,000 ton vessel sailing to a neighbouring port.

Return Period(year) 500 1000

Risk Coefficient 1 1.4

Cont…..• A particular safety feature is that the minimum clearance from

sea level to the top of tunnel’s rock protection is more than 20m, which is well in excess of the 15m maximum draft of a 50,000 ton vessel.

CONSTRUCTION :- Soil improvement / foundation :-

• Marine clay is forming the sea bed except in the near shore areas where bed rock outcrops.

• The thickness of the marine clay along most of the tunnel alignment exceeds 20m.

• The major part of marine clay was “very soft to soft” and of “very high plasticity” to “extremely high plasticity”.

• To make the foundation more robust, soil improvement with cement deep mixing (CDM) and sand compaction piles (SCP) was chosen.

Typical CDM foundation layout at tunnel elements E3 to E14.

Plan view of CDM

Cement deep mixing (CDM)• Where the tunnel is placed in a trench ( E3 to E14) the clay was

strengthened with walls formed by contiguous columns of mixed cement and clay.

• The CDM columns were constructed using the wet mixing method, where cement slurry is mixed with the clay.

• The mixing shafts were first drilled with the rotating blades into the soil to the desired depth. The cement slurry is injected in the withdrawal stage, where the vertical speed of the machine and the flow rate of the cement slurry were kept constant.

• Four 1 m diameter columns with overlaps of 10 cm form a 1.9 m square column pattern. To form continuous walls, these square columns were placed with 10 cm overlaps in rows. The CDM walls reach depths of up to 60 m below sea level.

Mixing blades of the deep mixing machine and offshore CDM production barge

Sand compaction piles (SCP)

• Sand compaction piles are used where the tunnel was constructed on an embankment (E15 to E17).

• Sand compaction piles have been chosen in order to allow quick consolidation and strength gain of the clay.

• The SCP have a diameter of 2 m and reach depths of up to 65 m below sea level.

1. BusanKorea’s largest port2. Immersed tubeThe tunnel is 3.2km long3. Daejuk island Forms transition from immersed tube tunnel to bridge4. Jungjuk IslandStarting point for 919m cable stay bridge5. Two pylon bridge With 475m main span6. Jeo island Summer residence for South Korean president7. Three pylon bridgeWith two 230m main spans

Typical SCP foundation layout at tunnel elements E15 to E17.

Joints

• In consideration of the large water depths, the immersion and segment joints were both required to have a double water barrier.

• The immersion joint was designed as the conventional primary Omega seal and secondary Gina gasket configuration.

open position

close position

Construction of bridge The 29 superstructure spans for the approach bridges are up to 90 m long,

weigh up to 2,427 tonnes, composite with a 300-mm-thick concrete deck slab. After prefabrication at Obi Bay, the spans were skidded to the waterside for

transport to the site. The geology of the site generally comprises marine deposits (sandy and clayey

layers) overlying residual soil (formed by decomposing and weathering of the bedrock in places) and bedrock. The nature of the bedrock was variable and consists of Cretaceous mudstones, tuff, sandstones and granite.

The foundations for the Lot 1 bridge piers were cellular caissons founded on weak or hard rock, located in up to approximately 30m of water.

Viaduct and anchor pier shafts were precast concrete, and the three 103-m-high pylons are cast in situ with the legs providing a signature gentle curve in transverse elevation. The lower pylon legs taper inward toward the caisson foundations, reducing the plan area of the foundations.

Contd….

The foundations of Lot 2 is generally similar to those of the bridge in Lot 1, except for the presence of an ancient valley in the bedrock in-filled with approximately 18 m of marine clay.

Daejuk Island side of the bridge was supported by 16 and 12 piles, respectively, each being 2 m in diameter by 60 m in length.

Each end segment was prefabricated at Obi Bay complete with its thickened concrete deck.

Being located in the open sea, the bridges were exposed to extreme wind and wave conditions from typhoons so based on this experience, the bridges were designed for wave heights of up to 13 m with critical wind speeds up to 80 m/s, and wind affects on the partially built structures were closely analysed.

Project cost

Total cost -1.8 billionGovt. subsidy- 0.45 billionBy consortium-1.35 billion lead contractor- Daewoo Engg. & Construction company

• Project has been designed for service life of 100 years.

ADVANTAGES:

Economic use of shape (cross section)Vertical clearanceSoil condition:- advantages for a soft soil condition when

a bridge support is difficult Capable of dealing with seismic effect

CONCLUSIONBusan-Geoje Fixed Link locates in an exposed offshore, which is subjected to strong winds, large swell waves and strong tidal currents. Thus, the design and construction conditions are very challenging and a number of traditionally used solutions for immersed tunnels not usable. Therefore, the design and construction have been developed in order to overcome a number of difficult conditions.

These kind of projects like Busan-Geoje fixed link, Millau viaduct, palm Island are wonders of new era. So as an engineer we can say that with the help of our knowledge and technology we can create more wonders like Busan-Geoje Fixed Link.

REFERENCES

• [1] http://www.roadtraffic-technology.com/projects/busan

• [2] http://www.strukton.com/projects/busan-geoje-fixed-link/

• [3] http://www.industrytap.com/drive-through-the-deepest-immersed-sea-highway/7892

• [4] https://www.youtube.com/watch?v=zKJNZTS1Gco

• [5] www.google.com