Abstract: To study the stressinfluencing factors of the segments during shield tunneling through the round gravel stratum of Yuanjiang River in Changde, China, the internal forces on the segment structure and stratum water pressure at the segment ring with the highest waterhead on the east line tunnel are obtained during segment assembling and shield passing through. The synchronous grouting pressure and shield jacking force are also extracted and are compared and contrasted with the internal forces on the segment. The following conclusions are drawn from the study: (1) The synchronous grouting significantly affects the internal force on the segment, mainly by affecting the stratum water pressure. The first three groutings most severely impacts the internal force of the segment after decoupling. (2) The jacking force negatively affects the internal force on the segment, mainly in the longitudinal direction. (3) When the segment force becomes stable, the circumferential axial force and bending moment reach 3 700~5 000 kN and -200~200 kN·m, respectively, and the longitudinal axial force reaches 0~2 500 kN, indicating a large axial force, small bending moment, and good health of the segment.

Key words: underwater shield tunnel, round gravel stratum, water pressure, jacking force, segment force