A rectangular shaft 6 × 8 m is planned for a depth of 1,500 m where the premining stresses relative to compass coordinates (x=east, y =north, z = up) are given by: σxx = 1,724 + 11.3h, σyy = 5,517 + 4.5h, σzz = 2.49h, where h is depth in meters and stress is in kPa; compression is positive. Find the best shaft orientation (explain), then determine if shaft wall support is needed at some depth. Wall rock properties are: E = 42.8Pa, ν = 0.33, c (cohesion) = 38.6 MPa, φ = 52◦, γ = 25.0kN/m3.