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December 27, 2022

Midas GTS NX: Excavation by Tunnel Boring Machine in 3D FEM






TBM is becoming one of the most common tunnel excavation methods in cities with limited space because other methods such as open-cut or NATM have problems of traffic obstruction, contamination by noise and vibrations, in addition to the large space requirements for support structures. The TBM method has the advantage of limiting disturbances in nearby terrains as well as automatically installing the tunnel walls. This significantly reduces the cost and makes it ideal for use in urban areas or for long distance tunnel projects. 


Segment Exterior Excavation vs Interior Excavation vs Shield, Grout



This training will focus on the key aspects of setting up a TBM model for 3D analysis by the finite element method using MIDAS GTS NX. It will also show other benefits of modeling tunnels in GTS NX such as activation of initial rock stresses, water pore pressure, tunnel lining contraction, as well as the use of the Stage Wizard to easily set up repetitive construction stages.

The tutorial uses '2D Shell Plate' elements to model the shield TBM and the concrete grouting, and uses 'Solid' elements to model Segments. During the Shield TBM excavation, it is assumed that the excavation pressure (HP) and the Jack thrust (J) are applied on the shield excavation face. The Shield external pressure(S) and segment external pressure (E) are applied around that face.
Since the data of this tutorial is simplified for the purpose of analysis process acquirement, it might be different with a real project application.

2D Shell Plate Model


Lastly, the training will show the advance post processor features of GTS NX to inspecting and extracting results from the analysis in both table and graphical formats. Results for displacements during excavations, stresses on tunnel linings, changes in rock stresses and even seepage results will be inspected.

Shell Stress



Presentation Slides







Key Points
• Shield TBM tunnel modeling
• Apply internal and external radial pressure and directional thrust loads
• Tunnel Wall Contraction load
• Initial stress, water pore pressure set up
• Setting construction stage using CS Wizard
• Parametric Analysis set up for material parameters comparison
• Analyze Results – Generation of displacement in each construction stage.





Speaker :  MIDASoft, Inc.

Category : Geotechnical

Software : midas GTS NX

Date : 2018-02-08




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