Soil Mechanics - Seepage of Soils

1. If a liquid(say water) is flowing through the soil mass, then flow force of the liquid is called
(a) seepage pressure
(b) effective pressure
(c) friction force
(d) all of the above

2. Seepage force per unit volume can be expressed as
(a) i{\gamma _w}L
(b) iL
(c) {\gamma _w}h
(d) i{\gamma _w}
where i is hydraulic gradient, L is length of soil sample, h is hydraulic head and {\gamma _w} is unit weight of water. (GATE 1996)

3. Seepage pressure always acts 
(a) against the direction of flow
(b) in the direction of flow
(c) perpendicular to flow
(d) none of these

4. If seepage pressure becomes equal to submerged weight of soil, then
(a) net effective stress becomes zero
(b) soil becomes cohesion less
(c) soil looses all its shear strength
(d) all of the above

5. Seepage velocity of a soil is given by formula
(a) discharge velocity/void ratio
(b) discharge velocity/porosity
(c) discharge velocity x void ratio
(d) discharge velocity x porosity

6. A soil has a discharge velocity of 6 x 10⁻⁷ m/s and a void ratio of 0.5. Its seepage velocity is
(a) 18 x 10⁻⁷ m/s
(b) 12 x 10⁻⁷ m/s
(c) 6 x 10⁻⁷ m/s
(d) 3 x 10⁻⁷ m/s (IES1995)

7. At a certain moment seepage pressure becomes equal to submerged weight of soil. Now if seepage pressure is slightly increased, then soil particles start lifting and move in the direction of flow. This phenomenon is called
(a) quick condition
(b) boiling condition
(c) quick sand condition
(d) all of the above

8. The hydraulic gradient corresponding to quick sand condition is called
(a) boiling hydraulic gradient
(b) effective hydraulic gradient
(c) critical hydraulic gradient
(d) none of these

9. If G is specific gravity and e is void ratio of soil, then critical hydraulic gradient is given by
(a) \frac{{G + 1}}{{1 + e}} 
(b) \frac{{G - 1}}{{1 - e}}
(c) \frac{G}{{1 + e}} 
(d) \frac{{G - 1}}{{1 + e}} (AMIE Summer 97)

10. A deposit of fine sand has porosity “n” and specific gravity of soil solids is G. The hydraulic gradient of the deposit to develop boiling condition of sand is given by
(a) {i_c} = (G - 1)(1 - n) 
(b) {i_c} = (G - 1)(1 + n) 
(c) {i_c} = \frac{{G - 1}}{{1 - n}}
(d) {i_c} = \frac{{G - 1}}{{1 + n}} (IES 1996)

Answers

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

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