土木工程外文翻译---釜山——巨济的交通系统：沉管隧道开创新局面-建筑结构(编辑修改稿)

土木工程外文翻译---釜山——巨济的交通系统：沉管隧道开创新局面-建筑结构(编辑修改稿)内容摘要：

aejuk island with a width of 1800 m and a depth of 18 m. For this navigation channel no height restriction is accepted by the Authorities and as such a tunnel has been the obvious way to cross. For the two secondary channels located between Jungj ukJeo island and JoeGeoje island, a minimum width of 435 m and two times 202 m, clearance heights of 52 and 36 m respectively are required. Water depth for both secondary channels is 16 m. The relative steep shores of Daejuk island and Gaduk island and the deep position of a bored tunnel of about 25 to 30 m below the seabed make it physically impossible to fit an alignment for 2020 届土木工程（隧道及轨道）毕业设计外文翻译 11 a bored tunnel in between these two islands. The gradient of the alignment would be too great and slopes too long for driving fort and safety. For this reason the crossing by an immersed tunnel with its position just under the seabed has been a logical choice. Figure 3. Longitudinal section of the link Geotechnical The geological strata vary along the tunnel alignment but top down typical consist of marine clay followed by marine sand and gravel on top of the bedrock. Marine clay is forming the seabed along the immersed tunnel alignment except in the near shore areas where outcrops of bedrock and shallow sand and gravel layers are found. The thickness of the marine clay exceeds 20 m along most of the immersed tunnel alignment. Most of the immersed tunnel will consequently be founded in this layer. The marine clay prises normally consolidated to slightly overconsolidated soft structured clays. These clays have been deposited during the Holocene epoch. The major part of the marine clay, from seabed down, is very soft to soft and of very high plasticity to extremely high plasticity. The marine clay plasticity index ranges from 56% to 85% with an average of 68%. The range of saturated unit weights of marine clay is to , with a mean value of N/ m3. Marine conditions The site is exposed to the Pacific Ocean via the Korean Strait and the Sea Of Japan at the South. This affects the marine conditions on site. An impression is given below by the 10000 years return period hydrological conditions for the south wave direction. The maximum design wave height Hs is 9,20 m and the corresponding mean wave period Tm is 15 sec. The principle wave direction due to typhoons is South. The current is mainly influenced by the tide, which is a typically semidiurnal type with a spring tide range of 1,60 m with a maximum current of m/sec at the tunnel alignment. The waves on site prise three main ponents: Locally generated wind waves, mainly from the northwest and northeast during the winter season。 Deep water generated wind waves, mainly from the South and South east, during the summer season。 Deep water swell waves, mainly from the South and South east. 2020 届土木工程（隧道及轨道）毕业设计外文翻译 12 During construction of the marine works the swell waves with a Hs of more than m and a period of 6 seconds have to be taken into account. In the summer season most of the time waves exceeds these values. Seismic conditions According to the Korean Research on Earthquake Design Standard the Busan – Geoje Fixed Link is classified as an aseismatic grade I structure with regard to the importance seisemicity of South Korea is mainly governed by the tsushima offshore and the yangsan onshore fault systems located in the depression between the Pohang Bay and Busan. However, only few major events have been recorded on those faults. This explain why, on a large scale basis, seismic hazard analyses leads to low hazards for Korea. The closest fault to the project site is the Yangsan onshore fault and the decisive (characteristic) earthquake will be an event on the Yangsan Fault at a distance of 510 km to the east of the project site and with a moment magnitude of . A twolevel earthquake hazard design approach has been adopted quake hazard levels are the operating design earthquake (ODE) and the maximum design earthquake (MDE). In respect of strength the MDE is regarded as Ultimate Limit State, but in order to survive seismic loads (prevention of major failure and maintaining safety) the MDE is regarded as service limit state, with the requirements that all joints shall remain watertight and rebar stress does not exceed yield strength fyk. tunnel39。 s special features In a number of ways the immersed tunnel part of the BusanGeoje Link is special and imposes a number of challenges. The alignment constraints impose a position above seabed at both outer ends of the alignment。 It is after the .resund Link between Denmark and Sweden the longest immersed concrete tunnel in the world。 The tunnel trench reaches to a depth of about 50m below mean water level。 The site is exposed to severe marine conditions。 The subsoil is characterised by its extreme weakness. And in addition to this the construction method by an unknown phenomenon in South Korea. Tunnel alignment From the deepest point the alignment climbs over 95m to the highest elevation of the cable stayed bridge over the main navigation channel. Maximum gradient is 4,73%, a little less pared to the gradient towards the east portal at Gaduk island which is 5%. Both exceed the maximum design gradient under standard conditions of 4%. The gradient at the west side of the tunnel alignment conflic。