Experimental Study on the Stress and Failure Mode of a Shield Tunnel Lining Under Asymmetric Thrust

This paper develops the "formation–shield tunnel segment–reaction frame model test system." The force and failure modes of the segment under different curvature radii and different left- and right-hand thrusts are compared and analyzed. The analysis results include the following. (1) Under asymmetric thrust, the axial force, bending moment, and deformation of the segment present an asymmetric distribution. With the increase in the ratio of the thrust between the lateral and inner jacks of the turn, the loading step of the damage inside the segment lining structure is advanced. (2) With the increase in the radius of curvature, the bending moment and deformation of the segment lining decrease, but the magnitude of the sudden change in the axial force of the segment structure increases accordingly. (3) The failure locations of the segment structure are mostly concentrated at the joints between the vault and the arch. With the increase in the jack thrust ratio, the cracks caused by segment structure failure also increase, transverse crack extension occurs where the force on the outside of the turn is large, and the peeling phenomenon occurs.