Factor of Safety from Forces
Easyslope stabilityfactor of safety
Resisting forces total 150 kN and driving forces total 100 kN. What is the factor of safety?
- A0.67
- B1.0
- C1.5
- D2.5
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Answer: C. 1.5
Equation: factor of safety FS = resisting forces / driving forces. Values: the resisting force, 150 kN, is the soil's shear strength acting up the slope along the slip surface. The driving force, 100 kN, is the weight component of the sliding mass pulling it down the slope. Step 1: FS = 150/100. Step 2: FS = 1.5, so the slope has 50% more resistance than it needs. 0.67 inverts the ratio (driving over resisting). 1.0 would mean the slope is exactly at failure.
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