A generic diagram of a slope in a jointed rock mass that is threatened by a planar block slide is shown in the sketch. With neglect of any seismic load, find the slope height (pit depth) possible with a safety factor of 1.15, given that Mohr–Coulomb failure criteria apply, the joints constitute 86% of the potential shear failure surface and: 

1 slope height                                      H =? ft (m);

2 failure surface angle                         α = 37◦;

3 slope angle                                       β = 48◦;

4 friction angle (rock)                         φ_r = 33◦;

5 cohesion (rock)                                 c_r = 2580 psi (17.79 MPa);

6 friction angle (joint)                         φ_j = 33◦;

7 cohesion (joint)                                c_j = 0.0 psi (0.0 MPa);

8 specific weight                                 γ = 162pcf (25.63kN/m³);

9 tension crack depth                          h_c = 0.0 ft (m);

10 water table depth                           h_w= 0.0 ft (m);

11 seismic coefficient                          a_o = 0.15;

12 surcharge                                        σ = 0.0 psf (kPa).