Abstract: In order to verify the safety of segment structure of large crosssection shield tunnel under high water pressure, 5 control crosssections of Sutong GIL utility tunnel project are selected as the research object to carry out prototype loading test on the segment structure by multifunctional shield tunnel structure loading device. Based on the theory of eccentric compression ultimate bearing capacity of concrete structure, MN bearing capacity curve of segment structure is derived, and safety evaluation index of segment structure is put forward. The research results show that: (1) The bending moment of the segment structure shows a butterflyshaped distribution, and the axial force shows a circularshaped distribution; the maximum positive bending moment and the maximum axial force appear on the crown. (2) The test internal forces of the segment structure of selected 5 control crosssections are all within the envelope of the bearing capacity curve, which is in a safe state. (3) The safety coefficient of the segment structure is unevenly distributed along the circumference; the safety coefficient of crown is smaller than other positions; the safety coefficient of segment structure ranges from 2.12 to 2.9, which meets safety requirements.

Key words: utility tunnel, underwater shield tunnel, segment structure, prototype test, MN bearing capacity curve, safety assessment