u2.04.06 How to dig a tunnel: excavation methodology

Summary:

This note proposes a methodology to simulate the digging of an underground gallery with Code_Aster. The basic method is a method commonly used in this kind of studies: the « convergence — confinement » method.

After a reminder of the principle of the method, the main steps of the Code_Aster command file are described. Various numerical examples make it possible to validate the procedure.

• 1. How to simulate the digging of a tunnel?
  • 1.1. Principle of the method, implementation and validation
• 2. Introduction
• 3. A method to simulate the digging of a gallery from a 2D model: the convergence-confinement method
  • 3.1. General principle
  • 3.2. Application of the method for a numerical calculation by finite elements
• 4. Before we tackle the Code_Aster command file…
  • 4.1. How do I define models based on a simple mesh?
  • 4.2. How do I initialize constraints?
  • 4.3. How to calculate the nodal reactions at the edge of the « future » gallery?
  • 4.4. How to simulate the creation of a « void » in the massif and the installation of concrete?
  • 4.5. Summary of proposed methods
• 5. Sample command files
  • 5.1. The problem treated
  • 5.2. Case no. 1: excavation without support with initialization of the stresses by a calculation and « softening » of the « excavated » elements
  • 5.3. Case n° 2: excavation with support with initialization of the constraints by calling CREA_CHAMP and deconfinement according to method A
  • 5.4. Case 3: excavation with support with initialization of the constraints by calling CREA_CHAMP and deconfinement according to method B
• 6. Validation of the Code_Aster on an example of excavation in a linear elastic medium
• 7. As a conclusion: advice and perspectives
• 8. Bibliography