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Ground fissure is a serious geological disasters, has a major threat to human daily life. In the ancient city of Xi'an in China, the ground fissure across the city has reached 14, which is being built in Xi'an Metro is a severe test. However, the history of the building of the subway project at home and abroad, there is no precedent in this type of venue construction subway, there is no off-the-shelf specification procedures to follow, so research crack mechanism and failure modes of the subway tunnel structure, a reasonable choice of lining structure, to find out how to ensure the overall stability of the lining structure under the influence of ground fissure, Xi'an subway construction engineering. In order to study the subway tunnel crossing ground fissure segment, ground fissure movement when the force mode and its surrounding soil pressure variations, the research group Chang'an University sedimentation test platform, horseshoe-shaped the subway tunnel structure through the cracks physical model tests. Tests the following conclusions: (1) tunnel structure through the cracks the local cracks on the plate settlement is completed, the default crack propagation, soil appears at the top of a lot of tension cracks, tension cracks in through the top of the structure and default cracks larger angle of about 20 °, there are a few along the longitudinal extension of secondary cracks, indicating that the impact of the structure of the crack extension have a certain impact, but also large axial structure rigidity. (2) from the model top surface of the soil deformation analysis of structure around the earth pressure distribution, structural stress and strain distribution, structure crack propagation observation of macroscopic phenomena, ground fissures activities of the tunnel structure through the cracks with the overall scope of major cracks in the vicinity of both sides, especially on the footwall near the crack band structure, ground fissure zones near the top of the structure in tension, the bottom of the pressure. Tunnel structure 40 ° cut through the cracks, and cracks on the plate decline will lead to structural torsion, bending, shear deformation and failure. (3) cross cracks integral tunnel structure will prevent the top of the structure the Rock downward movement of the body within a certain range, and decreased on both sides of the structure of the soil on the top of the structure of the soil body will produce a downward drag, which will greatly increase the vertical rock pressure of the top of the tunnel structure. In addition, the use of finite element software ANSYS numerical simulation on the horseshoe-shaped tunnel model, the numerical results with the results of the physical model test results show that the variation of the displacement, stress, strain consistent.
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