Circular Vertical Shaft Is Planned To Have Inside

A circular vertical shaft is planned to have a finished, inside diameter of 8 m in an underground hard rock mine. Rock properties are: Co = 189.0 MPa, To = 12.69 MPa, E = 42.69GPa, ν = 0.22, γ = 25.15kN/m3. The premining stress state relative to compass coordinates is: SE = 4,138 + 6.79h, SN = 1,379 + 9.05h, SV = 25.34h, where E, N, V refer to compass coordinates (x=east, y = north, z = up), h is depth in m, stress is in kPa and compression is positive. Premining shear stresses are nil relative to compass coordinates. Properties of concrete are: compressive strength = 37.93 MPa, tensile strength = 3.79 MPa, Young’s modulus = 37.93GPa, Poisson’s ratio = 0.25. Find: the concrete liner thickness in the vicinity of a water bearing cavernous dolomite where the pressure in the undisturbed ground is 1.45 MPa. Note: the maximum allowable compression in the concrete is 24.14 MPa.

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