| Application | PLAXIS 2D |
| Version | PLAXIS 2D CONNECT Edition V22.01 and V22.02 PLAXIS 2D 2023.1 PLAXIS 2D 2023.2 and later |
| Original Author | Richard Witasse - Application Engineer |
| Date created | 01 November 2022 |
| Date modified | 07 June 2024 |
The project considered here is related to the construction of a tunnel for the construction of a new metro line. The tunnel will be excavated at a relatively shallow depth using the conventional method (NATM). From available in-situ geotechnical investigation, excavation will mostly be taking place within green clay (referred to as montmorillonite clay) and marl. The excavation will be done in full section using an advancement length of 1 m.
Figure 1: Tunnel excavation for the new metro line construction
The tunnel is to be excavated in a very dense urban environment, with buildings sensitive to settlements. To reduce the displacements generated in the rock mass after excavation and thus the associated surface settlements, stabilization means composed of an umbrella vault and fiber glass bolting to the front is to be put in place (but not considered in the present PLAXIS analysis though). The support system, at the back of the front, is made up of steel arches and shotcrete. The installation of the steel set is done as close as possible to the excavated front.
As part of the tunnel design process in a dense urban environment context, geotechnical designers must not only properly assess the surface settlement during construction but also provide a safe design of the temporary support in the main section for both shotcrete and steel girders as shown in figure 2.
Figure 2: PLAXIS 2D support capacity diagrams for the tunnel lining
Main goals
Create the PLAXIS 2D model using the tunnel designer
- Evaluate equivalent homogenized plate properties for the temporary tunnel lining
- Simulate the excavation process using the confinement-convergence method through the Deconfinement soil feature
- Evaluate structural forces for each tunnel lining components and plots associated support capacity interaction diagrams
Requirements
To run this tutorial case, you will need the following:
- PLAXIS 2D CONNECT Edition V22 Update 1 or later
- Python files are available in the Downloads section of this article and it includes:
- The TunnelCompositeSectionLibrary.pyw script to create the equivalent homogenized plate for the tunnel lining
- The TunnelSupportCapacityPlot_Output.pyw script for calculating and displaying the structural forces in each individual component (shotcrete and steel girders) of the temporary tunnel support lining along with the support capacity interaction diagrams
Usage instructions for Python script
To use this Python script:
- Download the package from Downloads below
- Extract the zipped package and copy the content TunnelCompositeSectionLibrary_Input.pyw, TunnelSupportCapacityPlot_Output.pyw and shared.py files to:
[PLAXIS 2D installation directory]\pytools\shared - In PLAXIS 2D Input, create the equivalent homogenized plate for the tunnel lining using the TunnelCompositeSectionLibrary_Input.pyw script
- Run the PLAXIS 2D analysis and upload corresponding results in PLAXIS 2D Output program
- In PLAXIS 2D Output, the support capacity plots for previously defined tunnel linings can be drawn using the TunnelSupportCapacityPlot_Output.pyw script
If you do not have write access to add files to the PLAXIS 2D installation directory, you can use the following alternative approach:
- Save and extract the zipped package in a local folder
- Then, in PLAXIS 2D, go to Expert > Run Python script > Open … and browse for either TunnelCompositeSectionLibrary_Input.pyw or TunnelSupportCapacityPlot_Output.pyw depending on whether you are willing to create equivalent homogenized plate material set(s) for the tunnel lining(s) in PLAXIS 2D Input or looking to generating the support capacity plots in PLAXIS 2D Output.
Version
The script is tested with PLAXIS 2D CONNECT Edition V22 Update 1 and PLAXIS 2D 2023.1, PLAXIS 2D 2023.2 and later, with Python 3.8.
Download the Python files which are relevant to your PLAXIS version.
Disclaimer
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All software distributed under the PPL is provided strictly on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS OR IMPLIED, AND LICENSOR HEREBY DISCLAIMS ALL SUCH WARRANTIES, INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT, OR NON-INFRINGEMENT. See the PPL for specific language governing rights and limitations under the PPL.