Abstract: A prototype platform of a tunnel structure in a lowvacuum environment is used to test the sealing properties and surface strain of assembled shield segments under various conditions to improve the sealing properties of the segment structure. The following conclusions are obtained. (1) Vacuuming has little effect on the strain in the outer wall of the segment. The development of the strain in the inner wall of the segment during vacuuming can be divided into four stages, where the maximum tensile and compressive strains depend on the duration of the vacuuming stage. (2) The longitudinal assembly force has a larger effect on the sealing of the segment structure than the transverse assembly force. (3) The relative limit of the vacuum degree increases from 43 to 80 kPa after sealing improvement. (4) In theory, the existing segment structural gaskets can satisfy the airtightness requirements for a lowvacuum environment; however, the occurrence of assembly errors and limitations of practical construction technology require that the sealing and structure be improved and optimized.

Key words: low vacuum, shield tunnel, segment structure, sealing property, surface strain, prototype test