Research on Calculation Method of Segment Floating during Construction of Shield Tunnel

Shield tunneling method is widely used in subway tunnel construction because of its advantages such as not affecting ground traffic, high mechanization degree and short construction period. However, the problems of cracking and damage caused by uneven rising of segments are often encountered in the construction process of shield method, which affects the normal use of tunnel. However, the research on the mechanism and theoretical calculation of shield tunnel segment floating is relatively rare. In this paper, the floating mechanism of segments in the initial floating stage of shield tunnel is analyzed deeply, and the corresponding theoretical calculation formulas of upward buoyancy/anti-buoyancy and buoyancy are proposed. The theoretical calculation results are compared and analyzed with engineering examples. The results show that: The initial floating of the segment can be divided into two stages: rapid rising and slow rising, in which the rising amount of the rapid rising stage accounts for about 80%~90% of the total rising amount. The theoretical calculation value of the total floating amount is greater than the monitoring value, but the calculation error of the floating amount per ring is relatively stable, the theoretical calculation formula presented in this paper can provide reference for the calculation of the floating amount of the actual segment.