Abstract: To improve the bearing capacity, reliability, and safety of main bearing seal of largediameter shield (over 9 m), the structure, working principle, and properties of two main bearing seals are investigated, and case analyses are conducted. Then, finite element analysis is employed to study the contact stress of the seals, and the pressure and tunneling data of the two main bearing seals in dozens of largediameter shields are comparatively analyzed. The results reveal the following: (1) The bearing capacity of labiates seal structure with wedge protruding is higher than that without wedge protruding, which can bear excavation chamber pressure of no larger than 0.6 MPa without compensatory pressure. (2) Under the condition of excavation chamber pressure of larger than 0.6 MPa or momentary large fluctuation of excavation chamber pressure, the labiates seal structure is potentially brokendown due to delay operation or response of pressure compensation system. (3) The maximum positive dynamic bearing capacity of singlechannel fingertype seal is 1 MPa, thus the fingertype seal is recommended when the excavation chamber pressure ranges from 0.4 MPa to 1 MPa without arrangement of a pressure compensation system, which still can improve the bearing and pressurizing capacity of main bearing seal structure.

Key words: largediameter shield, main bearing, seal form, contact stress, finite element analysis