For a site, the design earthquake has the following parameters: Recurrence interval = 540 years…

For a site, the design earthquake has the following parameters: Recurrence interval = 540 years Richter’s magnitude = 7.2 Cyclic stress ratio = 0.23 The surface soil layer is a 30-ft-deep bed of fine sand with the following characteristics: Unit weight _ = 124 lb/ft3 Angle of internal friction = 34° Relative density = 0.85 The following results are produced by a laboratory test on a similar soil sample: Relative density = 95% Shear stress to cause liquefaction = 1,200 lb/ft2 The factor of safety for liquefaction, at a depth of 30 ft, is most nearly: A. 1.6 B. 1.9 C. 2.
For a site, the design earthquake has the following parameters: Recurrence interval = 540 years Richter’s magnitude = 7.2 Cyclic stress ratio = 0.23 The surface soil layer is a 30-ft-deep bed of fine sand with the following characteristics: Unit weight _ = 124 lb/ft3 Angle of internal friction = 34° Relative density = 0.85 The following results are produced by a laboratory test on a similar soil sample: Relative density = 95% Shear stress to cause liquefaction = 1,200 lb/ft2 The factor of safety for liquefaction, at a depth of 30 ft, is most nearly: A. 1.6 B. 1.9 C. 2.2 D. 2.5