Three-dimensional numerical modelling of shield tunnel lining

摘要

The most important problem of shield segment design theory is whether the design model can reflect the actual stress of the segment. The models for design calculations are classified by joint evaluations as follows: usual calculation method, modified usual calculation method, ring with multiple hinged joints calculation method and Beam-spring model calculation method. The usual calculation method assumes that the segmental ring is a ring with uniform bending rigidity, ignoring the decrease of rigidity at segment joints. Both the segment joint and the ring joint are not considered in the usual calculation method; In the modified usual calculation method a coefficient of effective ratio of bending rigidity (η ≤ 1) is introduced to evaluate rigidity of joints, a bending rigidity is represented as ηEI, also a transfer ratio of bending moment ζ is introduced, the moment of main section is calculated as (1 + ζ)M and the moments of the joints are calculated as (1 - ζ)M. Now the value of η and ζ are mainly determined by experiences in consideration of joint performance test results and past project records, which is random and uncertain; ring with multiple hinged joints calculation method is a method utilized under the good ground conditions. Segment joints are treated as hinges. The influence of ring joint is not considered, but the influence of segment joint is exaggerated; Beam-spring model calculation method assumes the segmental ring as a ring with rotational and shear springs. This is a method to evaluate reduction of bending rigidity and splice effects of staggered arrangement by using a model where a segment is considered as a curved beam or a straight beam, and a segment joint is as a rotational spring and a ring joint is as a shear spring.