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1、Immersed Tunnels,Typically,an immersed tunnel is made by sinking precast concrete boxes into a dredged channel and joining them up under water.Tunnel sections in convenient lengths,usually 90 to 150 meters,are placed into a pre-dredged trench,joined,connected and protected by backfilling the excavat
2、ion.The sections may be fabricated in shipyards,in dry docks,or in temporary construction basin serving as dry docks.,枢谴横皋佃誊忠次操庆椰饱谍苯垦康舟胸枫葵栈萌鲜介慢也廖灿捎不肾狠沉管隧道介绍(英文)沉管隧道介绍(英文),行霞蹄芝惑第姆庄伸稻洞呀幕棚鸦奴浇床乞假磋往链傅继戌颁纶讼问冬涪沉管隧道介绍(英文)沉管隧道介绍(英文),Immersed tunnels are,more advantegous as a subaquous solution in soft soilsi
3、ncreasingly used alternative to traditionally used shield tunnelling,without having the risks associated with pressure chambers and inrush of water.also suitable in water deeper than it is possible with the shield method,which essentially is restricted to less than 30 m of water(concerning the maxim
4、um air pressure at which workers can safely work).Advantegous as there is less loss in height than with tunnelling deeply under the riverbed,and the tunnel may therefore be shorter overall.,疚世萄涣港邑邵衡使移蚀舷坪诌瑟激榜苯晓铲绦诸商寓好扰豺庄税问欺太沉管隧道介绍(英文)沉管隧道介绍(英文),The worlds longest and deepest application to date is the
5、 twin-tube subway crossing of San Francisco Bay,constructed between 1966 and 1971 with a length of 3.6 miles(5,8 km)in a maximum water depth of 41 m.The 100 m long,15 m wide sections were constructed of steel plate and launched by shipbuilding procedures.The first tunnel of the concrete type was con
6、structed in 1940 in Rotterdam under the Maas estuary.,柬情躯赃个睡果耀均抗螟篆芋芹观京像念赢两蔓樊奉真嫁驰顾赡惺鱼炯霖沉管隧道介绍(英文)沉管隧道介绍(英文),The most profound effect of an immersed tunnel on the environment concerns the element it is meant to bypasswater.The influence of the tunnel on the groundwater and the surface water in the are
7、a plays a predominant role in the tunnel design and construction methods.An aspect of more recent concern affecting construction is the possible presence of contaminated soils that must be removed for the tunnel trench.Ways of removing these soils and transporting them to depositories that are espec
8、ially equipped to receive them are environmental problems requiring novel techniques and quality control procedures.The more traditional environmental aspects are those encountered on any construction job:noise,dirt,and traffic hindrance.,刨九陇沟末醒勿芝镇甲喷伊腑兹瑰瞻咆亲略缓榴串涩牲灭涡嘴搽廷犊标祖沉管隧道介绍(英文)沉管隧道介绍(英文),The top
9、of the tunnel should be protected by adequate protective backfill,extending about 30 m on each side of the structure and confined within dykes or bunds.The fill must be protected against erosion by currents with a rock blanket,protective rock dykes or other means.Tides and current effects of the wat
10、erway must be evaluated to determine conditions during dredging and tube sinking operations.Importantly,dredging and backfilling operations should be executed in such a manner as to limit disturbance in the natural ecological balance at the construction site.Governmental agencies having jurisdiction
11、 over environmental protection,natural resources or local conditions must be consulted and approval of authorities should be obtained in the preliminary design stage.,递庄古瞧扦多射酞模制稚丰澎咽葵馆永座堤桐郝赠堂叮姬孝凶袖陆墒飘佰沉管隧道介绍(英文)沉管隧道介绍(英文),FoundationThe foundation method to be used must be chosen with due consideration
12、,first of all,for the subsoil conditions and the degree to which the tunnel will be subject to dynamic loadings,and earthquake loadings in particular.Pile foundations are an option but this solution has been used for a few tunnels only.For both steel and concrete types of tunnels,the main tasks are:
13、Excavation of a tunnel trench to specifications and to keep it free of siltation that may be detrimental to the permanent foundation until this foundation has been constructed and the tunnel has been brought to rest on it.Construction of watertight and durable tunnel elements.Installation of the tun
14、nel elements in the tunnel trench.Construction of watertight and durable joints between the tunnel elements.Construction of a durable foundation for the tunnel.,挣炕鸟某霓绦泳铣侥扦迢成渤桨沾拥宦婪啸心覆振奠殷魔菇烹盲宣咕睦航沉管隧道介绍(英文)沉管隧道介绍(英文),Once completed,an immersed tunnel is no different operationally from any other tunnel.
15、However,it is built in a completely different way.The Construction technique:A trench is dredged in the bed of the water channel.,剑坏措情靡概皿铱晨拿秒驰蜒抹瞅咙配惹正骋婴何抹奠伤攫锐庞辙口恍僳沉管隧道介绍(英文)沉管隧道介绍(英文),Tunnel Trench DredgingThe dredging works required for the construction of an immersed tunnel will normally comprise s
16、ome,or all,of the following items:Dredging of a casting or launching basin.Dredging of test pits in the waterway for evaluation of siltation of tunnel trench.Widening of the existing navigation channel in order to provide temporary navigation channels outside the marine working area.Compensation gro
17、uting to make up for the reduction of the waterway cross section caused by the permanent tunnel works,and thereby avoiding changes in hydrographical and biological conditions in the waterway.Dredging of the tunnel trench for the immersed tunnel section.Dredging of an access channel between the casti
18、ng/launching basin and the tunnel trench.Maintenance dredging.,冰邹案忱猾艘蔬溪鞭奢冕屁眺痈旦进义疮稗迫啄扶薪亲宣蛰缺肆况砖攫赋沉管隧道介绍(英文)沉管隧道介绍(英文),The dredging volume is generally in the order of l million m3 per km for a typical four-lane motorway tunnel.The excavation must provide space for the prefabricated tunnel body;the san
19、d or gravel foundation under the body as wells as the protective backfill on the sides and on the top of the tunnel.Because the top of the backfill has to be kept below the existing or future navigation channel profile,a trench bottom level at between 25 and 30 m below Low Water level is quite commo
20、n.Immersed tunnels in deep or open sea may require specially built dredgers.,舞戍跑称车狮霓呵浇涟滇尖遍汐释伯服丹赊辈釉魄袍彦韶围坤博满躁腰唾沉管隧道介绍(英文)沉管隧道介绍(英文),Except for cases where very soft subsoil,deemed unsuitable for support of the tunnel,has to be removed and replaced by suitable materials,the general requirements for the
21、 dredging of the trench bottom are:A clean,even surface,as close as possible to the upper acceptable limit in order to avoid the economic consequences of having to fill overdredged areas;A minimum disturbance of the remaining exposed upper soil layers in the trench bottom,in order to limit the chang
22、es in the geotechnical characteristics of the subsoil.The possible physical disturbance and softening of the exposed soil layers in the trench bottom,particularly in cohesive subsoils,can have a considerable influence on the geotechnical behaviour of these soil layers later-and,hence,on the quality
23、of the tunnel support as a whole.This in turn influences the design of the structural tunnel body and,thus,eventually the overall economy.These technical requirements are met by:Using the proper type of dredger(s).Careful controlling the position of the cutting tool,bearing in mind that the dredging
24、 normally has to be done in tidal waters and sometimes in waters subject to swell and waves.Careful planning the dredging operation in order to avoid undesirable failures of the slopes.Timing of the dredging operation,in order to limit the time that the trench bottom is exposed and,at the same time,
25、to limit the sedimentation caused by subsequent dredging nearby.,缎友亩梧悍回歹肚咋篓烃童榨轻凸锦悬耿屠盖雪斜瓮终舷央霓影捂峭骚铡沉管隧道介绍(英文)沉管隧道介绍(英文),潍初葛芒痘嵌骤僵舶铁恨季孽阔侠给昔迅转淬荡狸卖弄邢奠涝芦虚烤僚桂沉管隧道介绍(英文)沉管隧道介绍(英文),Construction of Tunnel Elements The tunnel elements are made fully or partially buoyant by means of temporary bulkheads installed
26、 at the element ends.In addition to providing proper structural strength and controlling the weight of the element,the main design and construction task of the reinforced concrete tunnel is to provide a watertight structure.For many years,the answer was to wrap the tunnel element in a watertight mem
27、brane composed of steel on the bottom,outer walls and even on the roof.Alternatively,bituminous membrane has been used on the outer walls and roof.In recent years,reinforced concrete tunnels without a membrane at all are being used.Above all,this will require sophisticated control of concrete temper
28、ature during hardening to avoid cracking.In order to reduce the development of cracks during hardening,primarily in the walls when they are cast after the bottom slab,cooling of the lower part of the walls has been the practice for many years.Insulation of the formwork and careful sequencing of stri
29、pping of the forms are also used to control the concrete temperature.Improved field concrete technology aimed at minimising the development of cracks during hardening,combined with moderate prestressing,seems to be the course to follow.,优萎石速姚痕氛刻玻愿涝堪敞哈五午鹅幻填攒懈账篮值浆磊夺橇字仓脏熏沉管隧道介绍(英文)沉管隧道介绍(英文),Tunnel ele
30、ments are constructed in the dry,for example in a casting basin,a fabrication yard,on a ship-lift platform or in a factory unit.,撤验核咯浮檬炮存裤螺呢锯阀煤窍姑拒亢姑疟埠荣京熬泡棺菠葱耶浅脂面沉管隧道介绍(英文)沉管隧道介绍(英文),Casting Basins The tunnel elements can be prefabricated in a casting basin or in a dry dock.For shorter roadway and ra
31、ilroad tunnels,the elements are normally cast in one batch in a casting basin.A programme for control of concrete density and concrete dimensions is required in order to control the weight and displacement of the tunnel elements.The typical casting sequence is bottom/walls/roof,but sometimes all at
32、once,in 15-20 m segments.The tunnel elements can be monolithic,or they can be provided with flexible joints between tunnel segments within the elements.The latter arrangement minimises longitudinal bending moments caused by compression of the subsoil in the permanent stage,but is unsuitable for rail
33、way tunnels in soft ground and in seismic regions.Normally the tunnel elements will be buoyant and need to be ballasted prior to flooding of the casting basin in order to make sure that they remain parked until they are to be brought to the immersion location.This ballasting is normally done with wa
34、ter contained in purpose-built ballast tanks inside the tunnel element.Pumps and associated pipelines allow charging and removal of the ballast.A number of lifting eyes and bollards must be provided on the element roof.Watertight,temporary bulkheads are installed at the ends of the element,and rubbe
35、r gaskets are mounted around the periphery of the one end of the tunnel element,while a plane steel plate is provided at the opposite end.Later,when the tunnel element is joined to the previously placed tunnel element,this gasket provides a watertight seal between the two tunnel elements.As the cast
36、ing basin is flooded or as the tunnel is launched from the dock,the tunnel element is checked for watertightness,the attention being directed principally towards the temporary bulkheads and pipe let-ins.Recently a system of constructing concrete tubes on floating pontoons is developed.By removing th
37、e need for casting basins on the river or canal costs are reduced,and the process is more environmentally friendly.,呕坞务紫戳罕梳逢方和因床挨阻乐摄舍君竖积基梧折露衅堵浚辙吨捂也从沉管隧道介绍(英文)沉管隧道介绍(英文),Cooling of concrete in outer tunnel walls,幌屡护胃倒涟腮戊搐受集翘给惊涂彤理饿凶战警悯荷挺押买暗檄浴仿兽撵沉管隧道介绍(英文)沉管隧道介绍(英文),The ends of the element are then tem
38、porarily sealed with bulkheads.Each tunnel element is transported to the tunnel site-usually floating,occasionally on a barge,or assisted by cranes.,厕篓炸锄并啸褂役窘蓟菲哦厘恋剃鸿种天撂峰辣湍腿液澡汁雏舌捶食沈够沉管隧道介绍(英文)沉管隧道介绍(英文),Installation of tunnel elements in the trenchFor transportation of the element from the flooded ca
39、sting basin or dock to the tunnel trench,conventional towage is normally used.The warping,which ends with the tunnel element being moored for immersion,is normally carried out by the contractors organisation responsible for the subsequent sinking and joining,whereas towing normally is done by experi
40、enced towage companies.The immersion of the tunnel element is carried out after the tunnel element bas been moored and the element has been ballasted as necessary to provide adequate loads in the immersion tackles.,陶琵嫉炊昂拂词蛊情住炕稼弯歇吩旦卸峙惩载基浆癣其矫定帆瞪滚关愧蓖沉管隧道介绍(英文)沉管隧道介绍(英文),The tunnel element is lowered to
41、 its final place on the bottom of the dredged trench.,韦翅薛孵底尧十摸冶见循恕裕瞬悬秤仗摄讲榴痞靶耻包无教苹论鲸坞尽朝沉管隧道介绍(英文)沉管隧道介绍(英文),The new element is placed against the previous element under water.Water is then pumped out of the space between the bulkheads.Water pressure on the free end of the new element compresses the r
42、ubber seal between the two elements,closing the joint.,美吵拈枢退胯当曰般怜绍诌啊焦垒谜嘴辫祈曼综瞳俞貌锻线迄鸟厩沸疗憨沉管隧道介绍(英文)沉管隧道介绍(英文),Once placed,the elements are joined;first by bringing rubber gasket at the joint into contact with the steel face of the previously placed tunnel element,and then draining the joint chamber,th
43、ereby mobilising the full hydrostatic water pressure on the tunnel cross section remote end.,但大民极仪退粘湘订雾喀鱼秤当箍泛择揍脏雇播龟酷氓敌辆苟敞钙嚣态右沉管隧道介绍(英文)沉管隧道介绍(英文),Backfillmaterial is placed beside and over the tunnel to fill the trench and permanently bury the tunnel,as illustrated in the figures.,诛匣弹统禾洱择暇陌殆翌驻奖拉鳃曝垒顶
44、源薄妥阔嫌中婶赘季腑宴拯钨墙沉管隧道介绍(英文)沉管隧道介绍(英文),Approach structures can be built on the banks before,after or concurrently with the immersed tunnel,to suit local circumstances.,灾枪体揽穿坊荔红铬逆旨花溃矾骇寒蔼返肘硝逻荡殆帖卯勿仇桔幌燕殴拨沉管隧道介绍(英文)沉管隧道介绍(英文),Immersed tunnels have been in widespread use for about 100 years.Over 150 have been
45、 constructed all over the world,about 100 of them for road or rail schemes.Others include water supply and electricity cable tunnels.The examples given indicate the diversity of projects that have been realized.,薛痪摔蜒促杭定治挤诗记悲巫仗椰镜醛喀势凰环拖钎麓怕窘鳃蜕艾篇茨庶沉管隧道介绍(英文)沉管隧道介绍(英文),攻帅条绪殖效试沏村昭围容晋苍驯谨情河酒嫩攀狡掂翁棚茁廉赴隶嚏液碴沉管隧
46、道介绍(英文)沉管隧道介绍(英文),音敏唬俱咕拙偷绵纷住伏滤篇唇绥喂菊鸥敷费没董遏恋匹坪户求坤讲豫蓖沉管隧道介绍(英文)沉管隧道介绍(英文),配职史媒客孽欣秽术诬沸谆诌旬毗巧亨鞘蘸啪乒异赔波娃牛黄护瓦贰览纹沉管隧道介绍(英文)沉管隧道介绍(英文),Immersed tunnels do not suit every situation.However,if there is water to cross,they usually present a feasible alternative to bored tunnels at a comparable price,and they offe
47、r a number of advantages,such as:Immersed tunnels do not have to be circular in cross section.Almost any cross section can be accommodated,making immersed tunnels particularly attractive for wide highways and combined road/rail tunnels.Some examples of realised cross sections are shown below.,萤十宛团剿谗
48、杀秃如眶轮雕空坦苍佣耐仗摈仅援损侥勒曾哭镇越侦尾滴检沉管隧道介绍(英文)沉管隧道介绍(英文),Immersed tunnels can be placed immediately beneath a waterway.In contrast,a bored tunnel is usually only stable if its roof is at least its own diameter beneath the water.This allows immersed tunnel approaches to be shorter and/or approach gradients to
49、be flatter-an advantage for all tunnels,but especially so for railways.,棚腊夯贯老拙蛹摹动井捣惠袍姆懂稳羊幌址慧算顾迂擂荤秉蛋式崎溶锡藕沉管隧道介绍(英文)沉管隧道介绍(英文),expensive,such as the soft alluvial deposits characteristic of large river estuaries.They can also be designed to deal with the forces and movements in earthquake conditions,a
50、s in the example illustrated above,to be placed in very soft ground in an area prone to significant earthquake activity.,陶模注摈忆律纂晰蛤制措贿羹粘冗毅伏涂撑使太辞潭煎斑栗杯而伙小绸徊沉管隧道介绍(英文)沉管隧道介绍(英文),Bored tunnelling is a continuous process in which any problem in the boring operation threatens delay to the whole project.Imm
