Recently

in a working shaft more than 60 meters deep underground in Xiwan, Shenzhen

the cutterhead of the "Shenwan No. 1" shield machine broke through the soil

constructed by China Railway 14th Bureau Group

the Shenzhen Airport to Qianhai section of the Guangzhou-Dongguan-Shenzhen Intercity Railway

(abbreviated as the "Guangzhou-Dongguan-Shenzhen Intercity Ji-Qian Section")

the right line of the section from Shenzhen Airport to the Gushu working shaft was successfully holed through

This is the longest intercity railway subsea tunnel in China

The Guangzhou-Dongguan-Shenzhen Intercity Ji-Qian Section starts at the already-opened Shenzhen Airport Station of the Guangzhou-Dongguan-Shenzhen Intercity Railway and ends at the Qianhai Station comprehensive transportation hub. The line is about 15.2 kilometers long in total, entirely laid underground, with 3 stations: Xixiang, Bao'an, and Qianhai, and a design speed of 160 kilometers per hour.

The section from Shenzhen Airport to the Gushu working shaft is about 4.3 kilometers long in total, with a subsea crossing beneath Xiwan of about 3.1 kilometers. It is constructed using a slurry balance shield machine with an excavation diameter of 9.14 meters, and is the tunnel with the longest single-head excavation distance and the ** subsea crossing on the entire line, as well as the project with the highest environmental risk on the entire line.

The construction of this tunnel section overcame

geological conditions, risk sources, ultra-long distances, and

many construction challenges

It is a "high-difficulty" sea crossing

People say "under tremendous pressure"

but here the pressure is "sea"-sized

The tunnel crown is at most more than 60 meters below sea level

The shield machine drives over a long distance through high-pressure subsea strata

facing extremely high water and soil pressure

The shield passes beneath the Xiwan sea area of Shenzhen

The strata change like a "face-changing" act

This tunnel section densely crosses

cohesive soil layers, highly water-sensitive soil layers

upper-soft lower-hard composite strata, high-strength granite strata

and 9 types of strata in total

and the various strata change multiple times

Each time a stratum changes

special technical measures must be taken

The shield crossing multiple complex strata

is a contest of "hard against hard"

Long-distance driving in hard granite strata

with a maximum strength of 105 megapascals

requiring a force of three to four thousand tons to break the rock

Shield driving and segment assembly

Crossing densely distributed risk sources

Passing beneath the airport terminal staff dormitory building

Passing beneath the under-construction Shenzhen-Zhongshan Link

the Guangzhou-Shenzhen Yanjiang Expressway ramp bridge

……

Shield construction passes beneath many risk sources

In response to the construction difficulties and risks, the construction team of China Railway 14th Bureau Group fully drew on experience from shield tunnel construction crossing rivers and seas, repeatedly invited experts to review the construction technical plans, and successively overcame more than 10 technical problems, including mud cake formation on the cutterhead during excavation in extremely cohesive strata. Through targeted improvements to the shield machine's cutterhead wear resistance, slurry flushing, disc cutter fixation, and compressed-air balance systems, the excavation construction efficiency was greatly improved.

Closely monitoring settlement conditions

During the excavation process, the project team used an automated information monitoring system and an intelligent shield monitoring platform to strictly control excavation parameters and conduct real-time monitoring and analysis of the completed tunnel, ensuring that the shield machine smoothly passed beneath multiple risk sources.

The Guangzhou-Dongguan-Shenzhen Intercity Ji-Qian Section is an important part of the Guangzhou-Shenzhen main axis of the Greater Bay Area intercity railway network. After completion and opening to traffic, intercity trains will directly reach Qianhai and Bao'an Central, which is of great significance for improving the intercity network of the Guangdong-Hong Kong-Macao Greater Bay Area and realizing integrated regional economic development.