Comparison study of mechanical characteristics between conventional shield tunnel and shield tunnel with mortise-groove cross-section in ground fissure site

Under the condition of the shield tunnel intersecting the ground fissure section at a right angle, a physical model test was conducted at a geometric scale ratio of 1:30. This test aimed to compare and analyze the force and deformation of the conventional shield tunnel and shield tunnel after adopting measures to mitigate the effects of ground fissure dislocation. Meanwhile, a finite-element numerical simulation of a conventional shield tunnel under the same working conditions was performed. The physical model test results align closely with the outcomes predicted by numerical calculations. The deformation observed in the shield tunnel primarily consisted of vertical shear deformation near the ground fissure, accompanied by a minor torsional deformation. In grade IV ground fissure sites, both the conventional shield tunnel and shield tunnel with mortise-groove cross-section after taking measures exhibit a basic level of safety. However, only the shield tunnel, after taking measures, is safe when the ground fissure develops to grade III. By contrast, the conventional shield tunnel generates significant shear deformation at the first circumferential seam in the footwall of the ground fissure, which easily causes the joints inside the circumferential seam to yield shear. When the ground fissure grade was raised to II, the conventional shield tunnel and shield tunnel with mortise-groove cross-section after taking measures experienced relatively serious damage.