Stability evaluation of tunnels in steeply dipping layered rock mass using numerical models: a case study | JoVE Visualize

Stability evaluation of tunnels in steeply dipping layered rock mass using numerical models: a case study

Eleyas Assefa¹, Kidusyared Tilahun¹, Siraj Mulugeta Assefa¹

¹Department of Civil Engineering, College of Engineering, Addis Ababa Science and Technology University, Addis Ababa, Ethiopia.

Scientific Reports|January 15, 2025

View abstract on PubMed

Summary

Tunnel stability in steeply dipping layers is improved by understanding the stress relaxation factor (λ). This research shows how layer orientation and position affect tunnel deformation, enhancing the Convergence-Confinement Method (CCM).

Area of Science:

Geotechnical Engineering
Rock Mechanics
Civil Engineering

Background:

Tunnel stability is crucial in complex geology, especially with steeply dipping rock layers.
The Convergence-Confinement Method (CCM) is a 2D approach for analyzing pre-support relaxation but often neglects dipping layers.
Existing research primarily focuses on homogeneous or horizontally layered rock masses.

Purpose of the Study:

To investigate the impact of layer dip angle and position on the stress relaxation factor (λ) and tunnel deformation.
To enhance the accuracy of the 2D Convergence-Confinement Method (CCM) for steeply dipping, layered rock masses.
To provide insights for optimizing tunnel support in challenging geological conditions.

Main Methods:

Parametric analysis was employed to study the influence of geological factors.
Simulations were conducted to evaluate stress relaxation and tunnel deformation.
Comparison between 2D CCM predictions and 3D simulation results was performed.

Main Results:

The stress relaxation factor (λ) increases with steeper dip angles (60°, 90°).
λ decreases as layers are positioned farther from the tunnel center (e.g., two tunnel widths above/below).
Tunnel deformation is significantly influenced by layer dip angle and position.

Conclusions:

Optimized λ values improve the correlation between 2D CCM predictions and 3D simulations.
The study enhances the applicability of CCM for tunnel stability analysis in steeply dipping, layered rock masses.
Findings contribute to safer and more efficient tunnel design in complex geological settings.