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6 world firsts

recently, the construction of the zhangjinggao yangtze river bridge, the world's largest span suspension bridge under construction, has made important progress. the construction of the last small compartment of the south anchorage foundation of the south channel of the zhangjinggao yangtze river bridge has been completed. so far, the construction of 32 small compartments has been completed, setting the stage for the next stage of comprehensive this laid the foundation for carrying out large compartment construction.

the zhangjinggao yangtze river bridge connects the three cities of suzhou, taizhou and nantong in jiangsu province. it starts from the intersection of the shanghai-shaanxi expressway on the west side of rugao shizhuang town in nantong city, crosses jiangxinzhou (jingjiang minsha island in taizhou city), and ends at the zhangjiagang shugang expressway in suzhou city. the highway is connected to chenyang, with a total length of 30 kilometers and a total length of 7859 meters in the cross-river section.

schematic diagram of zhang jinggao yangtze river bridge route. picture/provided by interviewee

the zhangjinggao yangtze river bridge consists of the south approach bridge, the south channel bridge, the middle approach bridge, the north channel bridge, and the north approach bridge. among them, the southern channel bridge spanning the fujiangshan water channel of the yangtze river has a main span of 2,300 meters. it is the main bridge of the zhangjinggao yangtze river bridge and is also the longest span bridge under construction in the world. it has 6 spans, cable tower heights, and anchorage volumes. the first in the world, it is a world-class super project.

according to huang xiuping, deputy chief engineer of the technical center of cccc second harbor engineering co., ltd. and executive deputy chief engineer of zhang jinggao yangtze river bridge, the southern channel bridge of zhang jinggao yangtze river bridge across the main river has realized the transformation of china's bridge construction from a kilometer span to a two thousand meter span. the breakthrough in span is the first time that a chinese bridge has exceeded the span of 2,000 meters.

"worldwide, after bridge construction exceeds 2,000 meters, many technologies, standards and specifications are no longer available for reference. we have now actually entered the 'no man's land' of bridge construction." huang xiuping told china news weekly.

liu siqi, an assistant researcher at the comprehensive transportation research institute of the national development and reform commission, told china news weekly that the construction of the zhangjinggao yangtze river bridge will help cities such as nantong and taizhou connect with shanghai in a deeper way, and better integrate into the development of southern jiangsu, and improve the relationship between the suzhou-wuxi-changzhou metropolitan area and the coastal development belt. coordinate and link up to gather synergy for the development of the yangtze river urban agglomeration to further promote the integrated development of the yangtze river delta and the development of the yangtze river economic belt.

“more difficult than ever”

"the south channel bridge, the south main tower, the south anchorage, south to south, it's actually 'more difficult than more difficult'". when talking about the construction of the zhang jinggao yangtze river bridge, huang xiuping described the difficulty of its construction in this way.

rendering of zhang jinggao yangtze river bridge. picture/provided by interviewee

according to reports, the zhang jinggao yangtze river bridge has six "best in the world": it is the world's largest span bridge, the world's tallest cable tower, the world's longest high-strength main cable, the world's largest ground wall anchor foundation, and the world's longest continuous length of steel. box girder, the world's largest displacement telescopic device.

at the same time, the bridge also has six "world firsts" in its design: the first self-balancing structural system of the main cable of an ultra-long-span suspension bridge, the first ultra-high steel box-steel tube restrained concrete composite cable tower, and the first ultra-large-scale support-to-structure composite ground connection. wall anchorage foundation, the first hot-rolled l-rib partition continuous orthotropic steel bridge deck system, the first full-bridge integrated intelligent anti-corrosion system, and the first intelligent sensing replaceable anchor system.

in huang xiuping's view, behind every "world's best" and "world's first", there are new challenges for design and construction.

at the same time, the hydrological conditions of the yangtze river under the bridge have increased the uncertainty of bridge construction. there is a 12.5-meter deep-water channel in the lower reaches of the yangtze river. under the combined action of water flow dynamics and sedimentation, the swing range is about 1,890 meters over the years. how can the bridge span layout design cover the swing range of the 12.5-meter deep channel over the years and ensure that the bridge construction is not busy? the yangtze river shipping will have a greater impact, and full consideration must be taken into consideration during planning and design; the south tower is not in a deep water area, so how to overcome the possible "flood season reverse dryness" extreme weather and the impact of river sedimentation on foundation construction, during construction careful consideration is required before organizing.

as one of the first ultra-high cable towers, it is a landmark project of the south channel bridge of the zhangjinggao yangtze river bridge. as a world-class bridge, the zhangjinggao yangtze river bridge has extremely strict requirements for precision control.

the 350-meter-high main tower has a vertical deviation of no more than 87 millimeters, which is equivalent to the distance of only one fist. the main tower is composed of 30 segments, which requires the vertical deviation of each segment to be controlled within 2 mm, which is equivalent to the height of a 4-story building. the allowable deviation is only about the size of a mung bean.

during the construction process, huang xiuping was most impressed by the installation process of the steel tower of the first section of the south tower of the south channel bridge.

"one section of the steel tower has to pass through 166 small holes in the anchor rods at the same time. there is no precedent in the construction of a super-large bridge. if there is any problem with any anchor rod, it will lead to failure!" he said.

it is understood that the first section of the south tower needs to be tightly anchored to the concrete tower base through anchor rods, which is the most critical stress point of the main tower. the positioning accuracy of the first segment is crucial to the installation control of subsequent segments. therefore, the accuracy of anchor installation and steel tower manufacturing is a prerequisite for the accurate installation of the first section of the tower.

in order to accurately pass through the anchor rods, during the installation of the anchor rods, the horizontal deviation of the 166 anchor rods was controlled within 2 mm, and the verticality reached 1/4000; there are two layers of round holes in the first section of the steel tower. the minimum diameter of the round hole is 160 mm. the steel tower round hole is precision processed in the factory to ensure that the 140 mm anchor screw tip accurately passes through the two-layer steel plate round hole. after installation, it was measured that the maximum deviation of the axis was 2 mm and the maximum deviation of the elevation was 1.5 mm.

the installation and construction site of the first section of the south main tower of the zhangjinggao yangtze river bridge. picture/provided by interviewee

the foundation construction of the nanmaoding ground connection wall is another big challenge for the construction of the bridge.

the anchorage serves as the "big weight" for the suspension bridge to "steady the horse's steps" and plays the role of anchoring the entire main cable. construction is crucial, but how to meet the flood control requirements of the yangtze river waterway that large anchorage structures cannot be installed and build it but it is a big problem on the soft soil foundation like tofu.

the south anchorage wall of the south channel bridge is 110.05 meters long, 75.05 meters wide and 83 meters deep, which is equivalent to the size of 20 basketball courts and 28 stories high. it is the world's largest continuous wall anchorage foundation. the anchorage required pouring 550,000 square meters of concrete and used more than 58,000 tons of steel. the amount of steel used exceeded the amount of eight eiffel towers. due to its large size, deep depth, high precision, and new technology, it exceeded the existing construction specifications and many processes. there is no example to follow.

the construction site of the anchor area and tower area of ​​the zhang jinggao yangtze river bridge. picture/provided by interviewee

in order to ensure that the anchorage pulls up the weight of the entire bridge while the "footplate" is stable, the zhang jinggao yangtze river bridge built a huge "underground castle": the first support-to-structure composite ground wall anchorage foundation, with 47 rectangular "ports" the words are surrounded by numerous "small ground connecting walls" that are not connected but intertwined with each other. the structure forms multiple cabin structures of caissons, which are then connected into a whole by pouring retaining wall concrete to form a giant honeycomb underground. "castle".

huang xiuping described that the ultra-deep ground connection wall of the south anchorage requires that the verticality of the trench must be controlled within 1/800. in other words, a 1.5-meter-wide, 4- to 15-meter-long, and 83-meter-deep tunnel needs to be dug underground. the rectangular deep pit, with an upper and lower error of no more than 10 centimeters, is as difficult as using a large device to easily grab a coin on the ground on the top of a 30-story building.

what's even more difficult is that all of this work is done underground. once a section gets stuck, it's like a domino, and subsequent processes cannot advance.

fortunately, at the end of 2023, the last trough section of the zhang jinggao yangtze river bridge anchorage ground connection wall was successfully sealed and concreted, and the ground connection wall foundation construction of the entire bridge section was completed, marking the world's most difficult and complex ground connection wall foundation construction. the difficulty was successfully overcome. "although our anchorage project has created many firsts in the world, all the results are buried underground and cannot be seen or touched." huang xiuping said.

it is understood that the zhangjinggao yangtze river bridge is expected to be completed in october 2028. by then, it will only take 4 minutes to reach nantong from suzhou, making travel between the north and the south of the yangtze river more convenient.

solve the dilemma of "nantong is not connected to the south"

in march 2020, the national development and reform commission issued the "yangtze river main line cross-river channel layout plan (2020-2035)". a total of 8 river-crossing channel projects in nantong have received planning support. in the future, an "eight dragons crossing the river" pattern will be formed, zhang jinggao the yangtze river bridge is the "fourth dragon" in the "eight dragons crossing the river" pattern. it is also a key project for jiangsu to achieve regional complementarity, cross-river integration, and north-south linkage.

zeng gang, dean of the institute of urban development at east china normal university, told china news weekly that in the past, the yangtze river was regarded as a natural barrier that hindered exchanges between southern and northern jiangsu. many voices believed that the lagging development of northern and central jiangsu was the main reason. it's caused by traffic obstruction.

according to data released by the jiangsu provincial bureau of statistics, jiangsu province will achieve a gross product value (gdp) of 12,822.216 billion yuan in 2023. among them, suzhou city’s gdp in 2023 will be 2,465.34 billion yuan, the highest among cities in jiangsu province. it is the only gdp in jiangsu province to exceed 2 trillion city, accounting for 19.23% of jiangsu province’s gdp in 2023; at the same time, nantong’s gdp in 2023 will be 1,181.33 billion yuan, ranking fourth; taizhou’s gdp will be 673.166 billion yuan, ranking relatively low in jiangsu, and there is a big gap between nantong and suzhou.

when deploying key tasks for 2024, the jiangsu provincial government work report proposed to jointly promote the integrated development of the yangtze river delta and the high-quality development of the yangtze river economic belt, which clearly stated "planning and building the yangtze estuary industrial innovation collaborative zone."

zeng gang mentioned that many local management departments in jiangsu hope to strengthen the connection between the north and south sides of the yangtze river through the construction of cross-river passages, promote exchanges between northern jiangsu, central jiangsu, and southern jiangsu, and improve the core of the yangtze river delta while promoting economic integration. area and its edge areas.

liu siqi also pointed out that from the perspective of transportation, the construction of the zhangjinggao yangtze river bridge will help optimize the layout of the yangtze river main line crossing the river, improve the regional transportation network, effectively improve the ability to quickly cross the river, help nantong build the "eight dragons crossing the river" pattern, and deeply crack the the dilemma of "nantong is not connected to the south".

previously, nantong, located on the northern flank of the yangtze river delta, "near the river, the sea, and shanghai" had obvious location advantages. however, it was constrained by the natural chasm of the yangtze river. nantong's "south barrier" became a pain point and blocking point that affected economic and social development.

huang xiuping said that the most convenient way to get from nantong to suzhou is to take the sutong bridge and the shanghai-suzhou-suzhou yangtze river bridge. in the future, the zhangjinggao yangtze river bridge will serve as the most convenient passage between zhangjiagang and rugao, which will effectively alleviate the problems of the sutong bridge and the shanghai-suzhou yangtze river bridge. the yangtze river bridge and the congestion on the jiangyin yangtze river bridge.

public data shows that in 2023, investment in nantong's transportation construction will reach 41 billion yuan, with the total amount exceeding 40 billion yuan for the first time, exceeding one-seventh of the total annual investment in jiangsu province. it is obvious that nantong regards transportation as the “second line” of economic development.

zeng gang said that transportation is an important infrastructure, and improving transportation facilities has a positive impact on improving the business environment and will also help increase investor confidence. he said that regions in southern jiangsu, such as suzhou and wuxi, are already undergoing rapid transformation and upgrading. by improving transportation, jiangsu can accelerate economic ties between the north and the south and promote industrial transfer and cooperative development.

major infrastructure projects often have strong spillover effects. the total investment of the zhangjinggao yangtze river bridge is 31.167 billion yuan. zeng gang believes that while driving the development of related industries, the construction of the bridge will also have a certain driving effect on the local economy.

in addition, the improvement of transportation facilities will not only meet current travel needs, but also stimulate potential demand for passenger and cargo flows. "the connectivity and spillover effects after the completion of the zhangjinggao yangtze river bridge are worth looking forward to." zeng gang said, "for jiangsu, the return on investment in this kind of infrastructure is guaranteed."

it is reported that in the future, nantong will have one river-crossing channel every 20 kilometers on average, and nantong will be more accessible at that time.

liu siqi said that transportation is the "pioneer" of economic and social development, and the construction of the zhangjinggao yangtze river bridge will accelerate the cross-regional flow of resource elements and reduce the costs of logistics companies and corporate logistics.

he suggested that suzhou, nantong, taizhou and other relevant cities should jointly build industrial parks, jointly research key technologies, and jointly build value chains based on their own resource endowments and industrial development characteristics, such as strengthening advanced manufacturing, marine economy, textiles, medicine and other fields. the industry-university-research institute cooperates across the river to jointly cultivate a group of modern enterprises and comprehensive talents with core competitiveness, and jointly create a demonstration highland for cross-river integrated development.

author: chen shulian