Approximation method for yielding support analysis in high ground stress soft surrounding rock tunnels

Area of Science:

• Geotechnical Engineering
• Tunneling Engineering
• Rock Mechanics

Background:

• Analyzing soft rock and yielding support interaction in high-stress tunnels presents challenges in satisfying displacement coordination and static equilibrium.
• Existing mechanical analysis methods struggle with the complex interplay between rock deformation and support system behavior.

Purpose of the Study:

• To develop and validate novel approximation methods for calculating rock-support interaction in tunnels.
• To address the difficulties in simultaneously achieving displacement coordination and static equilibrium at the rock-support interface.

Main Methods:

• Mechanical analysis of rock and rigid support, incorporating radial displacement effects from yielding elements.
• Development of displacement approximation and support force approximation methods based on displacement coordination and static equilibrium.
• Curve fitting of numerical simulation and laboratory test results for yielding elements.
• Validation through calculations on two circular tunnel examples, comparing trisection, bisection, and substitution methods.

Main Results:

• The proposed approximation algorithms demonstrate high accuracy and reliability in calculating relative displacement and support forces.
• The bisection method exhibits superior stability and convergence compared to the trisection and substitution methods.
• Laboratory test data of yielding elements can be effectively utilized as direct computational data.

Conclusions:

• The developed approximation methods provide a reliable approach for analyzing rock-support interaction in tunnels.
• The bisection method is recommended for its enhanced stability and convergence properties.
• Further research is needed to address the influence of diverse geological conditions on the algorithm's effectiveness.