Design Equations for Predicting Stability of Unlined Horseshoe Tunnels in Rock Masses

This paper aims to propose new stability equations for the design of shallow, unlined horseshoe tunnels in rock masses. The computational framework upper- and lower-bound finite-element limit analysis is used numerically derive solutions this problems using Hoek–Brown failure criterion. Five dimensionless parameters including width ratio cover-depth tunnels, as well normalized uniaxial compressive strength, geological strength index, yield masses, are considered study. Selected mechanisms masses presented portray effect all parameters. New analyses developed technique nonlinear regression average bound solutions. proposed highly accurate can be with great confidence by practitioners.