A generic diagram of a slope in a jointed rock mass that is threatened by a planar
Question:
A generic diagram of a slope in a jointed rock mass that is threatened by a planar block slide is shown in the sketch. A minimum safety factor of 1.05 is required. Although not shown bench height is 60 ft (18.3 m). Determine if FS =1.05 is possible, given that Mohr–Coulomb failure criteria apply, the joints constitute 79% of the potential shear failure surface, slide block weight is 1.351(107) lbf/ft (198.6 MN per meter) of thickness and:
1 slope height H = 540 ft (165 m);
2 failure surface angle α = 32◦;
3 slope angle β = 45◦;
4 friction angle (rock) φr = 33◦;
5 cohesion (rock) cr = 2870 psi (19.8 MPa);
6 friction angle (joint) φj = 28◦;
7 cohesion (joint) cj = 10.0 psi (0.069 MPa);
8 specific weight γ = 158pcf (25.0kN/m3);
9 tension crack depth hc = 50.0 ft (15.2 m);
10 water table depth hw = 60.0 ft (18.3 m);
11 seismic coefficient ao = 0.15;
12 surcharge σ = 0.0 psf (0.0 kPa).
If FS < 1.05 will drainage allow the safety factor objective to be achieved?
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