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Hydro-Mechanical Analysis of Tunneling in Saturated Ground Using a Novel and Efficient Sequential Coupling Technique
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2024-10-31
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Edition:Final Report
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Abstract:Explicit coupling techniques are widely used in hydro-mechanical (H-M) analysis but require small time steps due to conditional stability. To improve computational efficiency, this report develops high-order alternating direction explicit (ADE) schemes for non-uniform grids under plane strain and axisymmetric conditions. These schemes, named SEA-4 and SEA-4-AXI, are integrated with the Fast Lagrangian Analysis of Continua (FLAC) geomechanical simulator, forming a new sequentially-explicit coupling technique. SEA-4 and SEA-4-AXI demonstrated significant improvements: reducing computation time to 20–66% of FLAC’s traditional method while maintaining high accuracy in pore pressure and displacement predictions. These results underline their value for efficient, accurate H-M simulations in tunneling projects. The report also explores how tunnel stability under surface loading is heavily influenced by liner permeability and the ground’s long-term H-M response. During tunnel advancement, the coupled interaction created a non-monotonic pore pressure pattern, temporarily confining the tunnel core—an effect absent in steady-state models. To capture this, two innovations are proposed: (1) an extended convergence-confinement method using transient unloading factors and (2) new equations for predicting the longitudinal displacement profile (LDP) using time-dependent constants. These equations reflect displacement profile changes due to H-M coupling, which conventional models cannot capture. Together, these advancements enable more realistic and efficient modeling of tunneling in saturated ground, with improved stability predictions and computational performance.
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[PDF-18.90 MB]
