### 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

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() is given by

(a)

(b)

(c)

(d)

5. For a soil mass, vertical coefficient of permeability() is given by

(a)

(b)

(c)

(d)

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 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 and are the permeabilities in x and z direction respectively in a two dimensional flow situation, the effective permeability is given by

(a)

(b)

(c)

(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)

**Answers**

1. (b) 2. (b) 3. (b) 4. (c) 5. (d)

6. (c) 7. (b) 8. (b) 9. (a) 10. (a)

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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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