Settlement rule of underpass railway model in shield tunnel and influence of nanomaterials on slurry performance during construction

In the shield tunnel, the phenomenon of structure penetration occurs frequently. Therefore, strict control of ground subsidence is imperative during the construction phase. In addition, other variables may be influence the performance of the slurry during the grouting procedure. This study aims to investigate and analyze the impact of nanomaterials on the properties of slurry used in construction, with the goal of determining the optimal construction route for the shield, ensuring quality construction of a U-shaped section, and meeting settlement control requirements. Firstly, the impact of double line spacing on the subsidence of U-shaped grooves is analyzed. Subsequently, the influence of common nanomaterials on slurry properties is examined through compressive strength testing. Among these nanomaterials, micro-silica powder exhibits the most significant enhancement effect on construction slurry performance with an optimal content of 5%. If the content of silica powder reaches 5%, the initial strength and later strength of the cement slurry will increase by 35% and 25% respectively, thereby promoting the enhanced performance of the slurry. In this study, the settlement of a U-shaped groove on the surface and subgrade is controlled by the settlement of a shield tunnel underpass railway model based on the distance between shield construction lines, providing valuable insights for future constructions with similar characteristics.