Scaled-down model test research on effective ratio of transverse bending stiffness for large-diameter shield tunnel

the effective ratio of transverse bending stiffness ( η ) is a key parameter in the modified conventional method for segments of large-diameter shield tunnel, and it significantly influences the internal forces of these segments. Based on similarity theory (with the tunnel joint relationship following the principle of equal stiffness ratio for segment joints), a geometric similarity ratio of C L = C p / C m =30.0 was selected. Model segments (made of HDPE material), transverse segment joint model bolts (made of PBT material), and longitudinal inter-ring joint model bolts (made of HDPE material) were used to construct three types of large-diameter circular shield tunnel test models: homogeneous rings, straight-jointed rings, and staggered-jointed rings. Using a self-developed loading device, graded loading tests were conducted on the three types of model segment rings. By comparing the vertical and horizontal radial deformations of the three test model tunnels, the value ranges of η were determined.