Calculate factors of safety and assess the stability of unsupported excavation using only conventional Kirsch equation for the following engineering data:
Tunnel: circular opening
Depth: 3,000 ft below surface topography
Diameter: 15 ft
Rock properties:
Density: 0.08 tons/ft3
Poisson's ratio: 0.2
Uniaxial compressive strength: 11,500 psi
Tensile strength: 7500 psi
Other derivate of Kirsh equation can be used but only after is mathematically prove that are derivate of it.
Calculate the stability of the two points on the excavation wall given on the sketch below.