Stability analysis of a square tunnel in cohesive-frictional soils using the stable node-based smoothed finite element method

This paper presents a stable node-based smoothed finite element method (SNS-FEM) based on the upper theorem of limit analysis for stability analysis of a square tunnel in cohesive-frictional soils subjected to surcharge loading. The homogeneous soil is considered rigid-perfectly plastic and obeys the associated flow rule following the Mohr–Coulomb failure criterion. In this paper, the square tunnel is subjected to the surcharge loading σs on the ground surface. The variations of the stability number σs/c have been investigated for different values of the cover depth-to-width ratio of the tunnel H/B, unit weight γB/c, and internal friction angle ϕ. Numerical results of square tunnels using the SNS-FEM approach demonstrate accuracy and efficiency. Design tables and charts of stability number results are provided for engineers to use in the preliminary design stage of the square tunnel.