Abstract: To explore the floating patterns of largediameter shield tail segments in high water pressure silty clay strata and its correlation with construction parameters, an indoor grout mixing proportion and property test and a field test in Yellow rivercrossing tunnel in Jinan, China are conducted. The results reveal the following: (1) Increasing the dosage of cement, fly ash, and waterreducing agent shortens the setting time of the grout, which is conducive to the decrease of segment floating. A decrease in the bleeding rate, fluidity, and consistency is unfavorable to segment floating control. (2) The floating of largediameter shield tail segments presents a parabolic. It quickly rises within 10 hours after synchronous grouting, then slows down rapidly, and becomes stable after 25－30 h. (3) The floating of segments are affected by various factors, it is recommended to dynamically adjust the grout mixing proportions, control the difference between of slurry discharged and entering volumes, reduce the cutterhead contact pressure, maintain the cutterhead torque, reduce the difference of thrust pressure between upper and lower section jack and synchronous grouting pressure difference, as well as appropriately extend the temporary downtime, driving and assembling time of the segment, and reduce tunneling speed.

Key words:  , tunnel engineering, large diameter, shield tunnel, segment floating, synchronous grouting, field test