NATM Tunnel Stress Relaxation Analysis

This tutorial guides you through modeling a two-dimensional NATM tunnel and simulating excavation-induced stress relaxation in MIDAS GTS NX. You will define Mohr-Coulomb rock, create the tunnel section, and model the initial and final liners using beam elements. You will apply self-weight and equivalent overburden pressure, establish the initial stress condition, and use load distribution factors to simulate progressive stress relaxation. After activating and replacing the tunnel linings in construction stages, you will examine settlement, plastic zones, grid forces, and lining forces. By completing this quest, you will learn how to: - Create and mesh a 2D NATM tunnel model - Define Mohr-Coulomb rock and elastic lining materials - Apply self-weight and equivalent overburden pressure - Establish the initial stress state using the K0 condition - Simulate progressive stress relaxation using load distribution factors - Sequence excavation and initial-to-final lining replacement - Review settlement, plasticity, and lining axial, shear, and bending forces

• Submit a model file based on the attached tutorial
• Submit a document with screenshots of the model settlement and vertical stresses