Civil Engineering MCQAE Level Civil Engineering
Rankine's coefficient of passive earth pressure K_p for a cohesionless soil with friction angle φ is:
Soil MechanicsPassive Earth PressureMEDIUM
Choose the correct answer
A
(1 - sinφ)/(1 + sinφ)
B
tan²(45° - φ/2)
C
tan²(45° + φ/2)
D
(1 + sinφ)/(1 - sinφ)
Correct Answer
D. (1 + sinφ)/(1 - sinφ)
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K_p = (1 + sinφ)/(1 - sinφ) = tan²(45° + φ/2). For φ=30°: K_p = (1+0.5)/(1-0.5) = 3. Note: K_a × K_p = 1 (they are reciprocals for Rankine's theory).
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