Experimental Verification on Stiffness Effective Rate for Shield Tunnel 3D Printing Model

［Objective］ In order to explore the feasibility of 3D printing technology in making tunnel models, it is necessary to determine the effective rate values of the shield tunnel longitudinal and lateral stiffness. ［Method］ Through tensile and compression experiments on photosensitive resin, epoxy resin and nylon three materials, photosensitive resin is finally selected as the model material for shield tunnel segments. Through the calculation of the second law of similarity, the experiment geometric similarity ratio is determined to be 1:30. The experiment is conducted based on Wenzhou M1 shield tunnel project, the tunnel model is finely designed using 3D printing technology, and the lining segments are connected with curved bolts to restore their detailed structure. By loading the 3D printed tunnel model to eight levels in longitudinal and transverse directions, the longitudinal and transverse stiffness efficiency of different assembly processes is determined. At the same time, ellipticityφ is used to specifically describe the lateral deformation degree of the tunnel under different external loads. Finally, by comparing with the model experiments of other scholars, the feasibility and accuracy of this method are demonstrated. ［Result & Conclusion］ The longitudinal stiffness efficiency of the through-seam shield tunnel made by 3D printing is between 0.13~0.20, and the transverse stiffness efficiency is 0.67; the longitudinal stiffness efficiency of the staggered seams is between 0.15~0.30, and the transverse stiffness efficiency is 0.79. The stiffness of staggered-seam tunnel is slightly greater than that of the through-seam tunnel. The ellipticities of the homogeneous tunnel, the staggered-seam shield tunnel and the through-seam shield tunnel are 1.62‰, 1.87‰ and 2.55‰ respectively. The through-seam tunnel model has the greatest degree of flattening under external loading.