Analysis of Segment Floating Law and Control Effect of Large Diameter Shield Segment in Shallow Overburden Soil

Large-diameter shield tunnels have been widely used in various river crossing traffic projects, and the problem of segments upward moving is prominent. Based on the Jinan Yellow River tunnel project, the middle section and the receiving section of the Yellow River were selected for on-site monitoring of segments upward moving, respectively. Combined with the indoor grout proportioning test, a comparative analysis of the law of segments upward moving of large diameter slurry shield tunnel in different test sections and the effect of treatment measures was conducted. The results show that when the large-diameter shield tunnel at the powdery clay formation is driven in the section with a buried depth of 2.5D and water pressure of 0.4 MPa, the process from the completion of segment assembly to uplift stability can be roughly divided into four stages: initial deformation stage (floating accounts for 22%), rapid floating stage (floating accounts for 55%), gentle floating stage (floating accounts for 28%) and slow settlement stage (settlement accounts for 5%); In the section with a buried depth of 1.6D and water pressure of 0.2 MPa, the percentage of segment elevation increments in each stage differed by 3%, 8%, -14%, and 3%, and the uplift period was extended by 2 times; The best time to control the segment uplift is within 10 hours of starting synchronous grouting and the comprehensive measures adopted in the project can effectively control segment uplift. Only grouting in the vault area has the most obvious control effect on segment uplift.