This twenty-sixth manual in the GEO5 engineering series provides a detailed guide to the numerical modeling of tunnel excavation using the New Austrian Tunneling Method (NATM) with the Finite Element Method (FEM) in GEO5. The manual focuses on the design and assessment of the primary lining of a single-track railway tunnel, taking into account the excavation sequence and the structural behavior of the tunnel lining under various conditions. Available for download, this manual is an essential resource for geotechnical engineers involved in tunnel design and analysis.

Learning Objective:

The goal of this manual is to teach users how to model and analyze the excavation and primary lining of a tunnel using GEO5 FEM software. Users will learn how to simulate the construction stages, assess the stress distribution, and evaluate the deformation and internal forces acting on the tunnel lining, ensuring that the design meets safety and performance standards.

Assignment Description:

In this assignment, users are tasked with developing a numerical model of a single-track railway tunnel and assessing the primary lining under conditions for speeds ranging from 160 to 230 km/h. The analysis includes modeling the tunnel excavation sequence (top heading, bench, and invert) and evaluating the primary lining made of C 20/25 sprayed concrete, supported by hydraulically expanded rockbolts. The manual provides step-by-step instructions for setting up the problem, defining construction stages, and interpreting the results for terrain settlement, lining deformations, and internal forces.

Outcome:

Upon completing this assignment, users will be able to accurately model the excavation and primary lining of tunnels using the NATM method in GEO5 FEM software. They will gain practical experience in handling complex construction sequences, interpreting the results of deformation and internal forces, and ensuring the structural integrity of tunnel linings under various loading conditions.

Conclusions:

The manual concludes that the use of FEM in modeling tunnel excavation provides detailed insights into the deformation behavior and internal forces within the primary lining. The results emphasize the importance of simulating the sequential excavation process accurately, as well as the need for local mesh refinement around critical regions. The analysis confirms that the modeled primary lining is capable of supporting the tunnel structure during and after excavation.

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