Civil Engineering - GATE Exam Questions - Discussion

12. 

A river 5 m deep consists of a sand bed with saturated unit weight of 20 kN/m3 . vw = 9.81 kN/m3. The effective vertical stress at 5 m from the top of sand bed is

[A]. 41 kN/m2
[B]. 51 kN/m2
[C]. 55 kN/m2
[D]. 53 kN/m2

Answer: Option B

Explanation:

No answer description available for this question.

Sadashiva said: (Jan 14, 2017)  
20 * 5 - 9.81 * 5 = 51.95.

Rakesh Kumar said: (Feb 3, 2017)  
Actually, it should be 50.95 KN/M2.

Phani said: (May 7, 2018)  
Here, it is σ = σ - u.

Vaish said: (Feb 24, 2019)  
20 * 5- 5 * 9.81 = 50.95kN/m^2.

Aqib Ahmed said: (Sep 1, 2021)  
Total stress= 20 x 5 = 100.
Pore water pressure = 9.8 x 5 = 49.
Effective stress = 100 - 49 = 51.

Basically, when the water tables fluctuate above the ground surface it will not increase or decrease the effective stress.

Effective stress will increase or decrease when the water table decreases or increases below the ground surface.

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