A Bridge that Connects the Mountains with the Plain

2021-05-14

Special Focus 2021年2期

关键词：钢混主塔长江大桥

Profile of the bridge prior to its completion合龙前的大桥一侧

The steel girders of the Chibi Yangtze Highway Bridge赤壁长江公路大桥的钢箱梁

在湖北省咸宁市三国赤壁古战场上游5 公里处，一座雄伟的跨长江大桥——赤壁长江公路大桥，2021年3月16日顺利合龙。

大桥建成通车后，将成为武汉城市圈和长江经济带重要的过江通道，从地跨湘鄂赣的幕阜山区到江汉平原，一步到达，将推动片区社会经济快速发展，成为推动湖北长江经济带发展的交通“硬支撑”。

一座大桥，承载半个世纪的期盼

赤壁，一个记载着千年厚重历史的城市，三国赤壁之战曾经发生在这里。如今，当年火烧赤壁遗迹历历在目。

万里长江蜿蜒流淌，滋养着赤壁这片美丽的土地，却也阻隔了两岸出行和经济发展。拥有128 公里长江岸线的咸宁却没有一座跨江大桥，是湖北省沿江城市中唯一没有跨江大桥的地级市。修建跨越天堑的长江大桥，成为两岸百姓多年的企盼。

2014年，国务院通过《长江经济带综合立体交通走廊规划》，嘉鱼和赤壁长江大桥双双列入长江干线新建过江通道重点项目。湖北交投集团主动请缨投资建设，咸宁跨长江大桥的梦想终于成真。

5 kilometers (about 3 miles)upstream of the ancient battlefield of the Three Kingdoms in Chibi,Xianning City,Hubei,the Chibi Yangtze Highway Bridge in all its grandeur spans across the Yangtze River,with its closure completed on March 16,2021.

After the bridge completes its construction and opens to traffic,it will become an important passageway across the Wuhan City Circle and the Yangtze River Economic Belt.It will enable smooth traverse from the Mufu mountainous area across Hunan,Hubei,and Jiangxi to the Jianghan Plain,expediting the social and economic development of the area and promoting the development of the Yangtze River Economic Belt with“infrastructural support” in Hubei transportation.

Half a century of hopes pinned on a single bridge

Chibi,a city with a thousand years of history,is where the famous Battle of Red Cliff took place in the Three Kingdoms Period (220-280).Today,the charred remains of Chibi are still freshly smoldering the collective consciousness of the people of the region.

The Yangtze River meanders for thousands of miles and nourishes the lush and lavish land of Chibi,but it also obstructs travel and economic development on both sides of the river.Xianning,which is home to 80 miles of Yangtze River shoreline,does not have a single bridge connecting the two shores.It is the only prefecture-level city along the river in Hubei Province that is impossible to cross without a boat.The construction of this bridge linking both sides of the river is long-anticipated by residents.

In 2014,the State Council approved the Comprehensive Plan for the Transportation Corridor of the Yangtze River Economic Belt,and the Jiayu and Chibi Yangtze River Bridges were both included in the key projects of the newly-built Yangtze River main line.The Hubei Communications Investment Group Co.,Ltd.volunteered to invest in the construction,and the dream of a bridge connecting Xianning had finally come true.

On March 21,2018,the sound of rumbling along the vast expanse of the Yangtze broke the calm serenity of the ancient battlefield that hearkens back to ancient clashes that took place more than 1800 years prior.The Chibi Yangtze Highway Bridge project officially broke ground that day.The dream of the Chibi Bridge that the people of Xianning had held so near and dear to their hearts for half a century had been made manifest.

Homegrown technology has made for a worldclass bridge

With a main span of 720 meters(2,400 feet),the Chibi Yangtze Highway Bridge is the world’s longest steel-concrete composite cable-stayed bridge in terms of span length.Experts believe that a breakthrough has been achieved in the main span of this bridge type,which has been effectively elongated from 1,900 to 2,400 feet with the closure of the Chibi Yangtze Highway Bridge.This has greatly enhanced the development of bridge-building technology and provides Chinese design and construction solutions for bridges all across the world.

The geological conditions at the bridge construction site are highly convoluted.The foundation is located on a limestone bedrock,from which karst caves are formed,the biggest of these is 51 feet.There are often water leakage and collapses during construction.The nature of the rock strata is poor,making it difficult to drill the foundation.

April 2020,the completion of the main pylons of the Chibi Yangtze Highway Bridge2020年4月，赤壁长江公路大桥主塔封顶

2018年3月21日，一望无际的长江岸边，隆隆的打桩声划破古战场1800 多年的平静，赤壁长江公路大桥正式开工，咸宁人民追求半个世纪的赤壁大桥梦成为现实。

技术植入，进入世界桥梁殿堂

主跨720 米！赤壁长江公路大桥是世界最大跨径钢混结合梁斜拉桥。相关专家认为，这一桥型的主跨实现由600 米级向700 米级突破，极大地推动桥梁技术发展，为世界桥梁提供了中国设计和建设方案。

赤壁长江公路大桥的桥址地质条件复杂，桩基位于灰岩区，溶洞发达，最大洞高15.8 米，施工常有漏水、塌陷现象，岩层性质差，桩基成孔难度大。

难，还在钢混结合梁的安装。整座大桥“骨架”由121 个主钢混梁组成。每片主钢梁包括2 根箱型主梁、3 根横梁、1 根纵梁和混凝土主桥面板，每个混梁重500 多吨，涉及多项复杂工艺，还要与斜拉索安装环环相扣，且每个“庞然大物”之间对接精度在3 毫米内。

作为大桥的主要受力结构，斜拉索安装是大桥建设的重要一环。赤壁长江公路大桥共设116 组232根斜拉索，采用钢丝强度达到1860兆帕。斜拉索单根最长387.21 米，最大重量38.49 吨。缆索的“穿针引线”也不轻松。“线”是一根重几十吨的斜拉索，里面绑着253 根钢丝，“针”是大型吊机，从223米高的主塔“穿”下来。工人在高空用张拉锚杆、卷扬机将盘卷的斜拉索吊起，把索头固定在主塔。索的另一头在桥面，用10 多个滑轮牵引，在吊机配合下将索穿进锚拉管。工人们穿一根“线”，要连续干3 小时。

承建单位是世界建桥实力派——中铁大桥局，团队加强技术攻关，实现了多项重要技术创新。在赤壁长江公路大桥上，两片主梁安装时间为12 天，比采用传统工艺缩短4 天，吊运一片梁比原来缩短3 小时，创造了“赤壁桥速度”。

大桥主塔采用“H”形设计，北主塔高217.33 米，南主塔高223米。项目创新设计方式，工艺工法创新取得了多个“世界第一”，攻克了大体积承台混凝土浇筑、超高主塔混凝土一次性垂直传输、大跨径720 米钢混结合梁索力和成桥线型控制等多项世界难题。

The bridge being outfitted with box girders建设中的赤壁长江公路大桥正在调装箱梁

Despite the difficulties,the installation of steel-concrete composite beams goes on as planned.The “framework” of the entire bridge is composed of 121 main steel-concrete beams.Each main steel-concrete composite girder includes two box-type main girders,three cross girders,one longitudinal girder and a concrete main bridge deck.Each composite girder weighs more than 500 tonnes and involves a host of complicated processes,and also requires installation with cable stays that interlock to 3-mm accuracy between each massive beam.

As the main stressed structure of the bridge,the installation of the stay cables is an important part of the construction.The Chibi Yangtze Highway Bridge has a total of 116 sets of 232 stay cables,with steel wire strength reaching 1860 MPa.The longest single-stay cable is 1,270 feet and the maximum weight is 38.49 tonnes.The “needlework” that fastens the cables is not easy,as the stayed cable weighs more than ten tonnes,and has 253 steel wires tied inside.The “needle”itself is a large crane that “sews”from the 730-foot-high main pylon.Workers use a tension anchor rod and crane to hoist the coiled stay cables to their soaring heights and fix the cable head to the main pylon.The other end of the cable is on the bridge deck,and it is towed by more than 10 pulleys.With the crane working in complete concert with the workmen below,the cables are inserted one by one into the anchor pipe.Workers “thread”nonstop for three hours to get each cable through.

The organization responsible for the construction is China Railway Bridge Bureau,a worldleading bridge construction group.The team has been bolstering its technical research and as a result,made a number of important technical innovations.On the Chibi Yangtze Highway Bridge,the installation time of the two main beams was 12 days,four days shorter than with existing technology.Meanwhile,the time taken to lift one beam was shortened by three hours,giving rise to something now affectionately called,“Chibi Bridge Speed.”

The main pylon of the bridge was formed into an H shape,the north pylon is 710 feet high,and the south pylon is 730 feet high.The innovations in design and technology for this project have achieved a laundry list of world firsts,and have overcome problems that have plagued bridge builders the world over,i.e.,large-volume pile cap concrete pouring,superhigh main pylon one-time vertical concrete transference,cable force of large-span 2,400-foot steel-concrete composite beams,and bridge linear control.(Translation:Chase Coulson)