Soil Mechanics Test 3

Result

Soil Mechanics Test 3

Score
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Rank
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Weekly Quiz Competition

Question 1
1 / -0

Which one of the following is correct in respect of pore water pressure u and effective stress σ, in the soil just below the bottom of a pond due to a 2 m rise in water level in the pond?

A
u increases by 20 kN/m² and σ remains unaltered

B
u increases by 20 kN/m² and σ decreases by 20 kN/m².

C
u decreases by 20 kN/m² and σ remains unaltered

D
Both u and σ remain unaltered

Solution

The rise in water level in the pond causes equal increase in total stress and pore pressure so effective stress does not change. The pore pressure will increase by 20 kN/m².
Question 2
1 / -0

The ratio of permeability of two soils having D₁₀ ratio as 2 is _______

A
4-4

B
44-41

C
47-46

D
49-42

Solution

Concept:
Allen Hazen’s formula: The coefficient of permeability of a soil is proportional to the square of representative particle size.
\(k = CD_{10}^2\)
Where, D₁₀ in mm and value of C lies between (0.4 – 1.2)
Calculation:
\(\frac{{{D_{10\;A}}}}{{{D_{10\;B}}}} = 2\)
\(\frac{{{k_1}}}{{{k_2}}} = \frac{{CD_{10\;A}^2}}{{C\;D_{10\;B}^2}} \Rightarrow \frac{{{k_1}}}{{{k_2}}} = {\left( {\frac{{{D_{10\;A}}}}{{{D_{10\;B}}}}} \right)^2} \Rightarrow \frac{{{k_1}}}{{{k_2}}} = 4\)