Resumen
In the construction of a shield crossing an existing mined tunnel without load, it is imperative to develop corresponding design standards that reflect actual engineering force characteristics to ensure the successful completion of the tunnel construction. This study uses the MIDAS-GTS NX 2022 finite element software to facilitate the creation of a numerical model of a shield structure for an air-push-over mine tunnel project in Changsha, China while investigating the stress field?s evolution during shield construction and calculating the maximum positive and negative bending moments and maximum axial forces for different structures and other force states under various construction conditions. This study?s findings informed the design and construction optimisation of a shield tunnelling empty-push method. The outcomes of this numerical simulation led to several key findings: (1) The soil density exerted a significantly greater impact on the internal forces of the initial support structure than both the tunnel depth and soil Poisson?s ratio. Additionally, a sudden shift in internal forces occurred within the 300?350 mm range when the lining thickness was altered. (2) Factors such as the tunnel depth, soil density, soil Poisson?s ratio µ, and lining thickness similarly influenced the internal forces of the segment and the initial support. Notably, the backfill layer thickness significantly affected the segment?s maximum axial force, causing an abrupt change of approximately 300 mm. (3) It is essential to control the guide rail?s thickness under the shield machine equipment?s weight constraint to prevent it from becoming overly large.