Generic Diagram Of Slope In Jointed Rock 1

A generic diagram of a slope in a jointed rock mass that is threatened by a planar block slide is shown, in the sketch. Although not shown, bench height is 55 ft (16.76 m).

Given that Mohr–Coulomb failure criteria apply, the clay-filled joints constitute 93%

of the potential shear failure surface, no tension cracks have yet appeared and:

1 slope height                          H =? ft (m);

2 failure surface angle             α = 32◦;

3 slope angle                           β = 49◦;

4 friction angle (rock)              φr = 38◦

5 cohesion (rock)                     cr = 1000 psi (6.90MPa);

6 friction angle (joint)             φj = 27◦;

7 cohesion (joint)                    cj = 10 psi (0.069MPa);

8 specific weight                     γ = 158pcf (25.0kN/m3);

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

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

11 seismic coefficient              ao = 0.00;

12 surcharge                            s = 0.0 psf (kPa)

Find the maximum pit depth possible without drainage.

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