With reference to the sketch of the potential slope failure shown in the sketch, find: Tension crack

With reference to the sketch of the potential slope failure shown in the sketch, find:

(a) The factor of safety of a cable bolted slope when the water table is drawn down 100 ft (30.5 m), bench height is 40 ft (12.2 m) (vertical bolt spacing), horizontal bolt spacing is 20 ft (6.1 m), the bolting angle is 5◦ down, and bolt loading is 700 kips (3.14 MN) per hole;

(b) The factor of safety of the same slope but without bolts when the water table is drawn down below the toe. The design trade-off here is between drainage and bolting, any reasons for preferring one or the other? A tension crack 37 ft (11.3 m) deep is observed at the crest behind the face. The slope is 320 ft (97.5 m) high, failure surface angle is 32◦, slope angle is 40◦, specific weight is 158pcf (25.0kN/m³), cohesion is 1440 psf (0.069 MPa), and the slide surface friction angle is 28◦.

Transcribed Image Text:

Tension crack Bench ft 40" B = 40° 100 | WT 320' 6 = 28° a = 32 -Failure Surface C = 1440 psf y = 158 pct Not to Scale