2. Introduction#

For several years, studies have been carried out with Code_Aster in order to model the behavior of geotechnical structures (earth dams, tunnels, engineered barriers for waste storage, etc.).

Code_Aster has already been used in particular to simulate the digging of galleries or wells, as part of the project Geological storage of nuclear waste HAVL (T4-01-10) or during previous studies on deep storage. The reports written so far (for example [6], [7], or [4]) naturally focus on the results, in order to answer the specific technical question that motivated the study. However, simulating an excavation using a finite element code is not necessarily an easy thing, and even if the general principles are recalled in the documents mentioned above, we finally find few elements on the structure of the command files that served as support for the calculations.

In order to help engineers in charge of future underground excavation studies with*Code_Aster*, this note provides some practical advice to get started in carrying out this type of calculation. Indeed, as part of the Storage project, MMC decided to fully adopt the approach implemented by AMA in 2000 and 2001. To achieve this, the entire approach was reproduced with version 6 of*Code_Aster*, based on a new mesh and by exploring some variants. MMC also benefitted from the assistance of AMA agents. In addition, this work resulted in a validation of*Code_Aster* based on classical analytical formulas in linear elasticity (Kirsch formulas and convergence-confinement method, [5]).

This report therefore presents:

  1. the classical method of simulating an underground excavation in 2D using a finite element code;

  2. the various options available to apply this method with*Code_Aster*;

  3. two Code_Aster validation test cases for underground excavation problems.

The prerequisite for a profitable reading of this note is basic training in the use of Code_Aster as well as a minimum of familiarization with the software package. The details of the various commands used are given in the Code_Aster User documentation (https://www.code-aster.org).