Upper Bound Solution of Safety Factor for Shallow Tunnels Face Using a Nonlinear Failure Criterion and Shear Strength Reduction Technique

Figure 5

Effect of and on the FOS for blow-out failure mechanism ( = 800 kPa, = 20 kN/m³, = 90 kPa, = 247.3 kPa, = 1~3, = 1.0~2.0).

(a)

(b)