A three-compartment rectangular shaft 3.7 × 7.4 m in cross section is planned for a depth of 914 m. The pre-sinking stress field is assumed to be caused by gravity only. The weakest rock along the proposed shaft route has an unconfined compressive strength of 55.17 MPa and a tensile strength of 5.17 MPa. Young’s modulus and Poisson’s ratio are estimated to be 31.0GPa and 0.25. Specific weight of rock is 25.6kN/m3. Determine the safety factors, with respect to tension and compression. What is the optimum orientation of the shaft?