Abstract: In order to study the mechanical response of shield tunnel segments in round gravel strata during construction period, a crosssection of Yuangjiang Rivercrossing Tunnel with the largest burial depth is selected to carry out test on internal stress variation characteristic and external water pressure of tunnel segment by continuous monitoring method, and comparison and contrast is made between monitoring data and simulation results. Main conclusions are drawn as follows: (1) The external water pressure of the segment structure is significantly affected by the construction of shield; the external pressure of ring 1 to 10 from the excavation surface fluctuates, and the time when the maximum value of different positions appears is different, which become stable after ring 10. (2) The axial force of the segment structure is mainly affected by the decoupling and grouting; the influence of the first three grouting is the most significant, and the influencing range is from ring 1 to 9; while the condition of bending moment is similar to that of axial force, but the influencing range by grouting is about 1 ring delay compared with the axial force. (3) The internal force of the segment is larger than the simulated calculation values, which indicates that the segment is affected by jacking force, hardening process of grouts and assembly effect. 

Key words: underwater shield tunnel, round gravel strata, segment structure, mechanical response, insitu monitoring