At 8:26 a.m. on August 7, when the quiet water surface in the shield receiving well was rippling, cheers were heard at the construction site. Under the strong support of the National 863 plan, the “world-class challenging project” designed and constructed by China Railway Tunnel administration, invested by CITIC Group, was officially opened, which also revealed the key technology of Shantou Bay Tunnel A comprehensive breakthrough has been achieved!

“after suffering from technology and mind, we have finally gnawed down this hard bone, and the construction of cross river and cross sea tunnel in China will usher in a new chapter!” Behind the confident and heroic words of Hong Kairong, chief engineer of China Railway Tunnel Bureau, is the painstaking efforts of 1560 builders on site for 816 days and nights, which is also full of the unrepentant efforts of academicians Qian Qihu, Sun Jun, Zhou Fengjun, Zhou Fulin, Wang fuming, Chen Xiangsheng, and many experts and technicians.

under the waves, the 15.03m super large diameter shield machine jointly developed by China Railway Tunnel administration, China railway equipment and China CITIC Heavy Industry Co., Ltd. drew a 3047.5-meter long submarine rainbow in the construction forbidden areas such as boulders, bedrock and 8-degree seismic intensity areas, successfully crossing the su’e Bay of Shantou.

Shantou is located in the east of Guangdong Province, where the three rivers of Han River, Lianjiang River and Rongjiang river flow into the sea. With beautiful scenery and superior geographical position, Shantou is an important node of the ancient maritime Silk Road and an important foreign trade port in Southeast China. However, due to the fact that Shantou is surrounded by mountains on all sides and separated into islands, it has been impossible to realize the interconnection of various districts since ancient times. In particular, the only inland bay in China, Suei Bay, divides Shantou into the north and the south. People face each other across the Bay and the traffic is extremely inconvenient.

although in the 1990s, Shantou built the Bay Bridge and the Boshi bridge, but up to now, only two bridges are far from meeting the traffic demand. In typhoon and rainstorm seasons, the dream of Chaozhou people to pass through both sides of the Strait all day long has never come true.

in the 21st century, with the continuous enhancement of the national economic strength and the rapid progress of tunnel technology, the century long dream of free travel of Chaozhou people has finally ushered in the dream realization moment – Shantou Bay Tunnel project has been put on the construction agenda.

from the first feasibility study conducted by 50 experts organized by the Department of communications of Guangdong Province in May 2008 to the completion of the west line tunnel of Shantou Bay Tunnel in August this year, Shantou Bay Tunnel has experienced 12 years.

Wang Mengshu, a famous tunnel scientist, an important founder of China’s subsea tunnel technology and a late academician of the Chinese Academy of engineering, participated in the related research of Shantou Bay Tunnel for many times before his death, which directly promoted the progress of the project.

“even at the last moment of my master’s life, I still keep in mind that I must build Shantou Bay Tunnel and make technical reserves for the future construction of channel tunnel in China.” Whenever he thinks of the Shantou Bay Tunnel, what Hong Kairong always thinks about is the earnest instruction of his teacher Wang Mengshu.

Shantou Bay Tunnel is located between Haiwan Bridge and Heshi bridge. The total length of the tunnel is 6680 meters. The length of the subsea tunnel is 3047 meters, with two-way six lanes and a design speed of 60 kilometers per hour. The submarine section is constructed by two super large diameter shield machines with diameters of 15.01 meters and 15.03 meters respectively.

Shantou Bay Tunnel is the largest cross sea shield tunnel in China, and also the first subsea tunnel constructed in an 8-degree seismic intensity area in China. The comprehensive difficulty is the peak of similar projects. It can be summarized in the following five words: “large”, “shallow”, “high”, “hard” and “dangerous”:

“large” refers to that the diameter of shield machine reaches 15.03 meters, which belongs to super large diameter; “high” refers to the location of high altitude The seismic intensity area reaches 8 degrees; “hard” refers to the boulder on shore section and bedrock section in the sea, with the rock strength up to 216mpa; “shallow” refers to the thin overburden layer above the shield machine, with only 8.2m overburden soil in the starting section; “dangerous” refers to that the Gulf tunnel is in a highly soft and hard uneven stratum, with extremely poor stability of seabed soft soil, great difficulty in construction and high safety risk, especially for shield machines The three sections that need to be crossed are 182 meters in length and the bedrock protruding section.

“the difficulties of Shantou Bay Tunnel lie not only in the five known challenges, but also in the endless unknown challenges. There is no reference for similar projects.” Nie Xuequn, chairman of CITIC City Development and Operation Co., Ltd., has a clear understanding of the difficulty of the project.

Qian Qihu, Sun Jun and Zhou Fulin, academicians of the Chinese Academy of engineering who have visited the site for many times to learn about the relevant situation, called the Shantou Bay Tunnel a “world-class challenging project”.

all kinds of debates about the construction of Shantou Bay Tunnel run through the whole project: bridge construction or subsea tunnel construction? Shield tunnel or immersed tunnel? Imported shield or domestic shield? In the face of seabed boulders and bedrock, is it to dig directly or to carry out pretreatment

especially in the selection of shield machine, whether it is the transportation department of Guangdong Province, Shantou Municipal government, or the construction unit CITIC Group, the design unit of Hunan Transportation Planning Survey and Design Institute, and the construction unit, China Railway Tunnel Bureau, etc., all bear great pressure and risk.

the shield machine was born in foreign countries. Today’s world-famous shield machine manufacturers, represented by German herrik company, have rich manufacturing achievements. Although China started the process of shield localization at the beginning of the 21st century, China Railway Tunnel administration, which undertook the National 863 project, successfully developed China’s first composite shield in 2008, but the application scope of domestic shield was limited, and there was no precedent for domestic manufacturing of 15m super large diameter shield.

one side is the imported shield with mature technology, and the other is the domestic shield which is growing and needs to learn nutrition from practice. Facing the “world-class challenging project” such as Shantou Bay Tunnel, the selection of imported shield can undoubtedly reduce the risk, and this scheme also occupies the mainstream among experts and technicians.

as the leader of the National 863 major scientific and technological project – “research and application of key technologies of super large diameter slurry shield”, Hong Kairong always has a dream to revitalize national industry: “as a high-end and complex equipment, shield machine is one of the representatives of” great power heavy equipment “, and an important embodiment of a country’s scientific research level, industrial manufacturing level and comprehensive national strength After decades of catching up, shield has made great progress. However, there are still many gaps to be filled in the domestic shield machine. One of the important reasons is that many people prefer to choose the mature imported shield machine, rather than bear the risks brought by the application of the domestic shield, so that the domestic shield missed many growth opportunities. ”

Finally, with the insistence of Hong Kairong’s technical team, the scheme of “one China and one foreign” two shield machines competing in the same field was confirmed, and the domestic shield machine entered the field of 15m super large diameter for the first time.

as a domestic shield manufacturer, Wang Dujuan, deputy general manager of China Railway Equipment Co., Ltd., has a different feeling in his heart: “domestic shield has been used for decades and has gone through nearly 200 years in developed countries. Shantou Bay Tunnel is the stage given to us by the times. What we have to do is to be worthy of this stage and the era.”

in April 2018, the imported shield started from the South Bank of Shantou Bay Tunnel, lasted 736 days, crossed Suai Bay, and successfully arrived at the north bank in May 2020.

in October 2018, the domestic shield also set sail from the South Bank of Shantou Bay Tunnel. It took 660 days to cross Suai Bay, and successfully arrived at the north bank in August 2020.

domestic and imported shield machines have successively started, driven in the same direction, and competed on the same platform. They jointly played the magnificent notes that astonished the world under the water of more than 20 meters in Suai Bay.

shield machine is a sharp tool for tunnel construction. Dozens or hundreds of cutting tools are distributed on the cutter head in front, which is equivalent to human teeth. Through the rotation of cutter head, the cutter cuts and grinds the obstacles in front, so as to realize continuous advance. The mud cake formed by cutterhead and cutter is a difficult problem that restricts the efficient tunneling construction of shield machine in viscous stratum.

when encountering soft clay cohesive stratum, cutterhead cutter is easy to deposit mud, and when encountering extremely hard rock stratum, it is easy to have abnormal tool wear and damage. Subsea tunnels usually encounter uneven soft and hard strata, and two conditions exist at the same time, one after another.

in order to deal with super hard rock more effectively, China Railway Tunnel Bureau has carried out a series of innovations, such as using heavy hob and widening blade thickness, upgrading gradient hardness design of cutter ring, anti backward monitoring device of atmospheric hob, optimization and innovation of installation of atmospheric hob cutter, forced anti loosening of cutter bolt, etc., and formed the theory of intelligent monitoring of cutter running state and evaluation of tunneling parameters With the key technology, the tool can be sensed, known and changed. According to statistics, a total of 225 times of cutter change have been carried out in the 182 m bedrock convex section of the eastern line of Shantou Bay Tunnel, and the average tool change is 2.5 times per 1 m.

every technical innovation is inseparable from the technical research on the construction site and the dedicated research of the rear research team. Chen Guangjiang, Secretary of the Party Working Committee of Shantou Bay Tunnel Project of China Railway Tunnel Bureau, recalled: “relying on the only State Key Laboratory for shield tunneling and tunneling technology in China, we will send the stratum samples collected on site to Zhengzhou for testing at any time. Every stone floating thousands of miles across the sea has finally become the targeted parameters, cutting tool design and protective measures for shield tunneling forward.”

on the stage of Shantou Bay Tunnel, a world-class challenging project, a number of cutting-edge research cross gathered: China Railway Tunnel Bureau, Guangzhou University and Southwest Jiaotong University jointly carried out seismic response law and seismic technology research of submarine super large diameter shield tunnel in high intensity seismic area; jointly carried out special research on shield machine design and manufacture with China railway equipment; and jointly studied with Central South University To study the key fire prevention technology of submarine single pipe extra long tunnel; to carry out research on the equipment and key construction technology of super large diameter shield in soil rock boulder mixed stratum with the State Key Laboratory of shield and tunneling technology and Tongji University

Kong Shaobo, general manager of Shantou su’e Channel Construction Investment Co., Ltd., attributed the successful promotion of the project to innovation and technology: “Shantou Bay Tunnel is not only a super project, but also a school and a laboratory. The stars of various industries gather together, and cutting-edge achievements in various fields are constantly colliding and integrating, which lays the technology for China’s long-distance and deep buried channel tunnel in the future Foundation. ”

the cross sea tunnel section of Shantou Bay Tunnel is located under the main channel in the sea. There are three bedrock bulges with a length of about 182 meters. The strength of the raised bedrock reaches 216mpa. In the face of ultra-high strength bedrock, many experts believe that it is not possible to directly excavate, so pretreatment should be carried out.

the technical team led by Hong Kairong carried out a series of rock breaking tests relying on the State Key Laboratory of shield tunneling and tunneling technology, and insisted on direct shield tunneling.

from July 8, 2019 to February 5, 2020, after carrying out targeted and bold innovation on cutting tools and cutter barrel, it took 156 days to finally pass through the bedrock convex section safely and smoothly, creating a precedent of using shield machine to directly pass through bedrock in China.

at first, many people in the industry were skeptical about the scheme of shield machine passing directly. As time went on, the doubts were gradually replaced by affirmation and admiration as the shield machine moved forward one meter one meter, which attracted a large number of research and observation teams. Looking at the shaped tunnel in front of you, the observation group marveled: “you got the ticket to build the channel tunnel first!