China's first ultra-shallow buried subway shield section under the tidal river penetrated through the seawater. Photo by Hu Yaojie
Qingdao, July 21 (Reporter Hu Yaojie) Qingdao Metro Line 4 Shalao section achieved a smooth double line breakthrough on the 21st, which is the first in China to penetrate the ultra-shallow buried subway shield section project of the tidal river under the seawater.
Li Zhihui, deputy director of the Engineering Management Department of Qingdao Metro Line 4 Company, said that the section is about 1115 meters long, and there are many first-level risk sources along the line, such as the South Jiushui River, a number of residential buildings, and a number of first-class risk sources such as soft and hard bad strata, which are technically difficult projects on the whole line and are the shield section with the highest risk in Qingdao Metro.
Li Xingjie, head of construction in the civil engineering 12 work area of Qingdao Metro Line 4 of the 24th Bureau of China Railway, said that the three sources of risk bring great danger to the construction, and this construction difficulty is like "dancing on the tip of the knife".
Construction workers are conducting a quality inspection of the segment assembly. Photo by Sun Fanggang
Li Xingjie said that the section diagonally crosses the South Jiushui River by 101 meters, the vault is buried 7 meters deep, about 200 meters from the mouth of the sea, the tide rises and falls twice a day, the deepest water level of the river is 3 meters at high tide, the groundwater has a hydraulic connection with the seawater, the tidal water level changes have a great impact on the shield boring, and the subway ultra-shallow buried shield section crosses the seawater tidal river for the first time in China. During the construction, according to the tide table, different parameters were used to excavate, double row rotary spray pile sealing and pouring cover were used to smoothly advance, which provided important engineering data for the construction of shield tunnels under tidal action.
Li Xingjie said that in the face of the lower penetrating housing group and the upper soft and lower hard bad formations (rock strength of 144Mpa), the project adopted the measures of advanced formation treatment, soil pressure and excavation control when advancing, increasing the amount of synchronous grouting and synchronously injecting auxiliary shield mud outside the shield body, doing a good job of settlement monitoring and geological radar scanning, etc., to achieve safe excavation, at the same time, the project also carried out the scientific research project research of "Shallow Buried Tunnel Shield Method Construction Through The Control Measures of the Upper Soft and Lower Hard Strata and the Settlement Law of Ground Buildings (Structures)". 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 expert consultation meetings many times to optimize the construction plan, formulate emergency plans, and finally successfully realize the double line of the Shalao section.
According to reports, Qingdao Metro Line 4 is the main trunk 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, and is scheduled to be completed and opened to traffic by the end of 2022. (End)
Source: China News Network