Consider a horizontal, rectangular opening that is 3 m high and 6 m wide and driven due north 1,524 m. Rock properties are, Co = 163.5 MPa, To = 10.2 MPa, E = 36.48GPa, ν = 0.27, γ = 25.34kN/m3. The premining stress state relative to compass coordinates is: SE = 2, 414 + 4.53 h, SN = 2, 897 + 7.92 h, SV = 25.34 h where stresses are in kPa, h = depth in m, E, N, V refer to compass coordinates (x = east, y = north, z = up) and compression is positive. Premining shear stresses are nil relative to compass coordinates. How wide can this opening be made before failure occurs at a depth of 533 m? Justify.