China News Service, Qingdao, July 21 (Reporter Hu Yaojie) Qingdao Metro Line 4 Shalao Section achieved smooth double-line connection on the 21st. This is China’s first ultra-shallow buried subway shield tunnel project underneath the seawater and tidal river. .

  Li Zhihui, deputy director of the Engineering Management Office of Qingdao Metro Line 4 Company, said that the section is about 1,115 meters long, passing through the Nanjiushui River, multiple residential buildings, and multiple first-level risk sources such as the upper soft and lower hard stratum along the line. , Is a technically important and difficult project for the entire line, and is currently the most risky shield section of Qingdao Metro.

  Li Xingjie, the construction leader of the 12th Civil Engineering Section of Qingdao Metro Line 4 of the China Railway 24th Bureau, said that the three risk sources bring huge risks to the construction, and this construction difficulty is like "dancing on the tip of a knife."

The construction personnel are inspecting the quality of the segment assembly.

Photo by Sun Fanggang

  Li Xingjie said that the section crosses the Nanjiushui River at an angle of 101 meters, the vault is buried at a depth of 7 meters, and the distance is about 200 meters from the sea entrance. The tide rises and falls twice a day. The water level of the river is 3 meters deep at high tide, and the groundwater and seawater are hydraulically connected. , The change of tidal water level has a great impact on shield tunneling. It is the first time in China that the super-shallow buried shield tunnel section of the subway crosses the seawater tidal river.

During the construction, according to the tide table, tunneling with different parameters, construction of double-row jet-grouting piles for sealing and pouring of cover slabs and other methods are smoothly advanced, which provides important engineering data for the construction of shield tunnels under the action of tides.

  Li Xingjie said that in the face of the under-crossing housing group and the upper soft and lower hard stratum (the rock strength is 144Mpa), the project has adopted the stratum treatment in advance, the soil pressure and the excavated volume control during the advancement, and the simultaneous grouting volume and synchronization Auxiliary shield mud was injected into the shield body, settlement monitoring and geological radar scanning were carried out to achieve safe tunneling. At the same time, the project also carried out the "Shallow tunnel shield method construction through the upper soft and lower hard strata control measures and ground construction. ) Research on the Law of Settlement of Buildings" to provide construction experience for similar projects in China in the future.

  It is reported that during the construction process, Qingdao Metro Construction Branch and the construction party held several expert consultation meetings to optimize the construction plan, formulate emergency plans, and finally successfully realized the double-line connection of the Sha-Lao Interval.

  According to reports, Qingdao Metro Line 4 is the main line of Qingdao's rail transit network, with a total length of about 31 kilometers, running through the east-west direction of the main urban area. It is planned to be completed and opened to traffic by the end of 2022.

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