5. Sample command files#
This part presents examples of Code_Aster command file structures concerning a circular excavation in an infinite and linear elastic medium, as part of a purely mechanical study (no coupling step THM). The cases presented here are the subject of validation test cases SSLP105A, SSLP105B and SSLP105C.
Three calculation cases are presented in this part:
an excavation without support with initialization by a calculation involving a fictional material to obtain the desired stress field (method \(I\));
an excavation with support, initialization of the constraints by a call to CREA_CHAMP and followed by the \(A\) method for deconfinement and the installation of the segments (\(\mathit{II}+A\) methods);
an excavation with support, initialization of the constraints by a call to CREA_CHAMP and followed by the \(B\) method for deconfinement and the installation of the segments (methods \(\mathit{II}+B\)).
For cases 2 and 3, the digging scenario is as follows: excavation, 50% deconfinement (\(\lambda =0.5\)), installation of \(30\mathit{cm}\) thick segments and end of deconfinement.
5.1. The problem treated#
The geometry of the mesh is mentioned in paragraph [§4.1]. It contains 8477 nodes and 3304 elements. The radius of the gallery is \(\mathrm{1,50}m\), the concrete thickness is \(\mathrm{0,30}m\) and the mesh is a square with a side of \(20m\). The rest of the data is summarized in the following table.
Material |
Parameter |
Value |
\({K}_{0}\) |
|
|
Rock |
\({\sigma }_{v}={\sigma }_{h}\) |
|
\(E\) |
|
|
\(\nu\) |
|
|
Concrete |
\(E\) |
|
\(\nu\) |
|
Table 5.1-1:Data from proposed test cases
Boundary conditions and loading are illustrated in the following figure:
Figure 5.1-a: Limit conditions and imposed loading
at the end of the lockdown process, \(\lambda =\frac{2\text{.}G}{{\sigma }_{0}\text{.}R}\text{.}{U}_{R}=\mathrm{0,}\text{69}\).
5.2. Case no. 1: excavation without support with initialization of the stresses by a calculation and « softening » of the « excavated » elements#
This example is relatively simple: it involves simulating an excavation without installing the support, with total deconfinement at the edge of the gallery. Therefore, only one model is used for the whole calculation.
The initial state is generated by a calculation (STAT_NON_LINE) that covers the entire mesh. The properties of the elements are affected according to the stress state that we want to reach (here \({K}_{0}\mathrm{=}1\) so \(\nu \mathrm{=}\mathrm{0,4999}\), the value of \(\mathrm{0,5}\) meaning the incompressibility of the rock cannot be used).
The following calculation concerns the nodal reactions at the edge of the future gallery. It is initialized based on the constraints from the first call to STAT_NON_LINE.
The last call to STAT_NON_LINE serves to reinject the nodal reactions into a model where the mechanical properties of the excavated elements have been very strongly weakened (\(E\) tends to \(0.\)). We then completely deconfine the field by making these reactions tend towards \(0\).
The command file corresponds to test case SSLP105C.
5.3. Case n° 2: excavation with support with initialization of the constraints by calling CREA_CHAMP and deconfinement according to method A#
The excavation scenario described above is followed. Only one model is used for the entire calculation. An additional STAT_NON_LINE command makes it possible to introduce the segments with realistic rigidity after a 50% deconfinement.
The command file corresponds to test case SSLP105B.
5.4. Case 3: excavation with support with initialization of the constraints by calling CREA_CHAMP and deconfinement according to method B#
The excavation scenario described above is still followed. This time, three models are used and an intermediate calculation (without physical reality, called a « bogus ») is necessary to transfer the variable fields from one model to another when setting up the segments after deconfinement by 50%.
The command file corresponds to test case SSLP105A.