Study on Segment Mechanical Properties of Shield Tunnel Obliquely Crossing Grade-Ⅳ Ground Fissures

Xi’an subway crossing ground fissures section adopts shallow mining method, and special measures are adopted in the structure. This kind of construction method and countermeasures are basically effective. Although the open cut method has many advantages, the ground fissures in Xi’an are mostly distributed in the urban area, and the open cut method has not been used to cross the ground fissure section. The two construction methods have outstanding problems such as impermissible construction conditions, long construction period, high construction risk, and high cost. To improve the construction safety, rapidity, and economy of Xi’an subway crossing the ground fissure section, this paper proposes the shield method to obliquely cross the grade Ⅳ ground fissure in Xi’an. Through numerical simulation, making a study on the mechanical properties of shield tunnel segment obliquely crossing grade Ⅳ ground fissure. The research shows the ordinary reinforced concrete segment now used cannot meet to require obliquely crossing grade Ⅳ ground fissure. After adopting the corresponding improvement measures of segment structure, waterproof material, and construction technology, it is found that the special-shaped thickening segment has strong feasibility in the ground fissure section, and the construction safety and economy are better than those of the traditional shallow mining method.