Study on the Applicability of Load Calculation Method for Large-Diameter Shield Tunnel in Argillaceous Sandstone Stratum under High Water Pressure

Surrounding rock pressure is an important factor to be considered during designing tunnel structures. In this research, the on-site surrounding rock pressure of a large diameter shield tunnel in argillaceous sandstone stratum was tested, and the evolution process of surrounding rock pressure was analyzed, based on which the variation law of surrounding rock pressure with buried depth and span of the tunnel was discussed. Combined with the numerical simulation method, the applicability of the load calculation method for the large-diameter shield tunnel in the argillaceous sandstone stratum was studied. The results showed that the variation of surrounding rock pressure generally changed from a rapid and substantial increase to a slight decrease and finally tended to be stable. Before reaching stability, the deformation pressure was dominant; then, the loosening pressure became the main pressure, and the surrounding rock pressure almost reached the maximum value in the synchronous grouting stage. Moreover, it was also found that the shield construction had a great influence on the surrounding rock pressure of the 15-ring segments behind the working face. While calculating the surrounding rock pressure, the tunnel section shape, buried depth and surrounding rock conditions should be fully considered. The Full Soil Column Theory, Terzaghi's Theory, Xie's Theory and Bierbauman's Theory were more suitable for tunnels with a buried depth of less than 2.5 hp. When the buried depth of the tunnel exceeded 2.5 hp, the calculation results needed to be enlarged by 2 similar to 3 times if the Statistical Method or Protodyakonov's Theory was used for calculation. Xie's Theory can be used to calculate the surrounding rock pressure of shallowly buried argillaceous sandstone stratum large-diameter shield tunnel. For a deeply buried argillaceous sandstone stratum large-diameter shield tunnel, it is recommended to use Numerical Simulation Method.