Tunnel Crown Stability Index

Assess tunnel crown stability using the Stability Number N (Broms & Bennermark) and calculate crown displacement using the Convergence-Confinement Method for shallow tunnels in soft ground.

2D stress state at a point. All stresses in MPa.

σx — Normal Stress X (MPa)
σy — Normal Stress Y (MPa)
τxy — Shear Stress (MPa)
⚙ Mechanical Note: Results are based on standard textbook formulas and ISO/AASHTO references. Always verify critical designs with applicable codes (ISO 898, AASHTO 1993, AISC, Eurocode 3) and a qualified engineer.
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How It Works

Assess tunnel crown stability using the Stability Number N (Broms & Bennermark) and calculate crown displacement using the Convergence-Confinement Method for shallow tunnels in soft ground

Each component has a specific meaning:

  • Stability Number N — The stability number n recorded for the patient or scenario being assessed.
  • Calculate crown displacement — The calculate crown displacement recorded for the patient or scenario being assessed.

Note: Interpret the tunnel crown stability result against the clinical thresholds and context described above.

How to Use

Enter the Stability Number N, calculate crown displacement for the patient or scenario you are assessing. Assess tunnel crown stability using the Stability Number N (Broms & Bennermark) and calculate crown displacement using the Convergence-Confinement Method for shallow tunnels in soft ground. Use the tunnel crown stability result to inform your clinical assessment.

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Frequently Asked Questions