Soil Mechanics - Permeability of Soil

1. Due to rise of temperature, the viscosity and unit weight of the percolating fluid are reduced to 80% and 98%, respectively. Percentage change in coefficient of permeability(k)
(a) 78.4%
(b) 22.5%
(c) 0 %
(d) none of these

2. Due to rise in temperature, the viscosity and unit weight of percolating fluid are reduced to 70% and 90% respectively. Other things being constant, the change in coefficient of permeability will be
(a) 20.0%
(b) 28.6%
(c) 63.0%
(d) 77.8% (IES 1996)
Hint: Taylor equation k = \frac{r}{\mu }.\frac{{{e^3}}}{{1 + e}}{C_D}^2

3. The coefficient of permeability of a soil is 5 x 10⁻⁵ cm/sec for a certain pore fluid if the viscosity of the pore fluid is reduced to half, the coefficient of permeability will be
(a) 5 x 10⁻⁵ cm/sec
(b) 10 x 10⁻⁵ cm/sec
(c) 2.5 x 10⁻⁵ cm/sec
(d) 1.25 x 10⁻⁵ cm/sec (GATE 1991)

4. For a soil mass, horizontal coefficient of permeability({k_H}) is given by
(a) \frac{1}{{{H^2}}}\left( {{k_1}{H_1}^2 + {k_2}{H_2}^2 + ..{k_n}{H_n}^2} \right)
(b) \frac{1}{{{H^3}}}\left( {{k_1}{H_1}^3 + {k_2}{H_2}^3 + ..{k_n}{H_n}^3} \right)
(c) \frac{1}{H}\left( {{k_1}{H_1} + {k_2}{H_2} + ..{k_n}{H_n}} \right)
(d) \frac{H}{{({H_1}/{k_1}) + ({H_2}/{k_2}) + ..({H_n}/{k_n})}}  

5. For a soil mass, vertical coefficient of permeability({k_V}) is given by
(a) \frac{1}{{{H^2}}}\left( {{k_1}{H_1}^2 + {k_2}{H_2}^2 + ..{k_n}{H_n}^2} \right)
(b) \frac{1}{{{H^3}}}\left( {{k_1}{H_1}^3 + {k_2}{H_2}^3 + ..{k_n}{H_n}^3} \right)
(c) \frac{1}{H}\left( {{k_1}{H_1} + {k_2}{H_2} + ..{k_n}{H_n}} \right)
(d) \frac{H}{{({H_1}/{k_1}) + ({H_2}/{k_2}) + ..({H_n}/{k_n})}}

6. A glacial lake clay deposit is found to have a series of silt partings in it at an average vertical spacing of 2 m. The silt layers are about 3 mm in thickness and have a permeability of 100 times that of clay. The ratio of the horizontal and vertical permeability will be
(a) 0.87
(b) 1
(c) 1.147
(d) none of these

7. A stratum of soil consists of three layers of equal thickness. The permeabilities of top and bottom layers are K = 10⁻⁴ cm/s and that of middle layer is K = 10⁻³ cm/s. Then the value of the horizontal coefficient of permeability {k_H} for the entire soil layers is
(a) 2 x 10⁻³ cm/s
(b) 4 x 10⁻⁴ cm/s
(c) 3 x 10⁻⁴ cm/s
(d) 1.5 x 10⁻⁴ cm/s (IES 1994)

8. A bed of sand consists of three horizontal layers of equal thickness. The value of Darcy’s k for the upper and lowers layers is 1 x 10⁻² cm/sec and that for middle layer is 1 x 10⁻¹ cm/sec. The ratio of the permeability of the bed in the horizontal direction to that in the vertical direction is
(a) 10 to 1
(b) 2.8 to 1
(c) 2 to 1
(d) 1 to 10 (IES 1996)

9. If {k_x} and {k_z} are the permeabilities in x and z direction respectively in a two dimensional flow situation, the effective permeability {k_e} is given by
(a) {k_e} = \sqrt {{k_x}.{k_z}}
(b) {k_e} = \sqrt {{k_x}/{k_z}} 
(c) {k_e} = \sqrt {{k_x} + {k_z}}  
(d) none of these (GATE 1999, AMIE Summer 97)

10. For a given soil mass, the average coefficient of permeability is 10⁻³ cm/sec and coefficient of permeability in horizontal direction is 5 x 10⁻³ cm/sec. The coefficient of permeability in vertical direction is
(a) 1 x 10⁻⁴ cm/sec
(b) 5 x 10⁻⁴ cm/sec
(c) 2 x 10⁻³ cm/sec
(d) 5 x 10⁻³ cm/sec (IES 1992)


    1. (b)    2. (b)    3. (b)    4. (c)    5. (d)
    6. (c)    7. (b)    8. (b)    9. (a)    10. (a)

These questions are taken from the book "Objective Questions (Civil Engineering)". The Kindle edition of this book is available at just ₹ 99/- only! 


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