### Soil Mechanics - Seepage of Soils

1. A flow net is drawn to obtain
(a) seepage, coefficient of permeability and uplift pressure
(b) coefficient of permeability, uplift pressure and exit gradient
(c) exit gradient, uplift pressure and seepage quantity
(d) exit gradient, seepage and coefficient of permeability (IES 1995)

2. The possibility of quick sand condition will be there when flow of water to soil is
(a) horizontal
(b) upwards
(c) downwards

3. Piping can occur in a soil mass when
(a) upward acting seepage pressure ≥ downward acting submerged weight of the soil above it
(b) upward acting seepage pressure < downward acting submerged weight of the soil above it
(c) upward hydraulic gradient approaches unity
(d) (a) and (c)

4. Piping in soil occurs when
(a) the soil is highly porous
(b) sudden change in permeability occurs
(c) effective pressure becomes zero
(d) the soil is highly stratified (GATE 1996)

5. Hydraulic gradient at exit is called
(c) piping
(d) none of these

6. The permissible exit gradient for safety against piping which endanger the stability of a hydraulic structure, should be
(a) 0.2
(b) 0.4
(c) 0.6
(d) 0.8

7. Total quantity of seepage per unit width perpendicular to section is (fields are elementary squares)
(a)
(b)
(c)
(d) none of these
Where  is number of flow paths(flow channels),  is number of equipotential drops, H is total head lost and k is coefficient of permeability.

8. If the flow net of a Coffer dam foundation had six numbers of flow channels and sixteen numbers of equipotential drops, with the head of water lost during seepage being 6 m through the foundation having k = 4 x 10⁻⁵ m/min, the seepage loss(in m³/day) per metre length of the dam will be
(a) 2.16 x 10⁻³
(b) 6.48 x 10⁻³
(c) 12.96 x 10⁻²
(d) 25.92 x 10⁻² (IES 1993)

9. A flownet of a Coffer dam foundation has 6 flow channels and 18 equipotential drops. The head of water lost during seepage is 6 m. If the coefficient of permeability of foundation is 4 x 10⁻⁵ m/min, then the seepage loss per m length of dam will be
(a) 2.16 x 10⁻² m³/day
(b) 6.48 x 10⁻² m³/day
(c) 11.52 x 10⁻² m³/day
(d)  34.56 x 10⁻² m³/day (IES 2000)

10. A flow net is drawn for a weir. The total head loss is 6 m, number of potential drops is 10 and the length of flow path for the last square is 1 m. The exit gradient is
(a) 0.6
(b) 0.7
(c) 1.0
(d) 1.6 (IES 1994)

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

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