Quick Sand Condition

Q. Quick sand condition occurs when

1. void ratio of the soil becomes 1.0
2. upward seepage pressure in soil becomes zero
3. upward seepage pressure in soil becomes equal to the saturated unit weight of the soil
4. upward seepage pressure in soil becomes equal to the submerged unit weight of the soil

Q.

What is non-cohesive soil? Give an example

Q. To provide safety against piping failure, with a factor of safety of 5, what should be the maximum permissible exit gradient for soil with specific gravity of 2.5 and porosity of 0.35 ?

1. 0.155
2. 0.167
3. 0.195
4. 0.213

Q. Consider the following statements:
1. Quick condition and liquefaction of saturated sands are based on similar phenomenon.
2. Quick condition is associated with only earth dams.
3. Liquefaction is possible in dry sand.
4. Liquefaction is associated with increase in pore water pressure due to vibrations.
Which of these statements are correct?

1. 2 and 4
2. 1 and 4
3. 1 and 2
4. 1, 3 and 4

Q. Foundation soil at the toe of dam has void ratio of 0.7. The specific gravity of soil grains is 2.6. To assure safety against piping, the upward gradient should not exceed 30% of gradient at which quick condition occurs. The maximum permissible upward gradient is

1. 0.282
2. 0.157
3. 0.09
4. 0.425

Q. The specific gravity and in-situ void ratio of a soil deposit are 2.71 and 0.85 respectively. The value of the critical hydraulic gradient is

1. 0.82
2. 0.85
3. 0.92
4. 0.95

Q. The range of void ratio between which quick sand condition occurs in cohesionless granular soil deposits is

1. 0.4 - 0.5
2. 0.6 - 0.7
3. 0.8 - 0.9
4. 1.0 - 1.1

Q. A deposit of fine sand has a 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

1. $i_{cr}=(G-1)(1-n)$
2. $i_{cr}=(G-1)(1+n)$
3. $i_{cr}=\frac{G-1}{1-n}$
4. $i_{cr}=\frac{G-1}{1+n}$

Q. A uniform sand stratum 2.5 m thick has a specific gravity of 2.62 and a natural void ratio of 0.62. The hydraulic head required to cause quick sand condition in the sand stratum is

1. 0.5 m
2. 1.5 m
3. 2.5 m
4. 3.5 m

Q. The relationship between the specific gravity of sand (G) and the hydraulic gradient (i) to initiate quick condition in the sand layer having porosity of 30% is

1. G = 0.7i +1
2. G = 1.43i -1
3. G = 1.43i + 1
4. G = 0.7i - 1

Q. A sand sample has a bulk density of $20kN/m^3$ and a degree of saturation of 70%. If the specific gravity of soil grains is 2.65, the value of critical hydraulic gradient for the soil will be

1. 1.02
2. 1.05
3. 1.10
4. 1.15

Q. A 3 m thick soil stratum has coefficient of permeability $3\times {10}^{-3}cm/secat{25}^{\circ }C$. Test results on same soil gives porosity 30% bulk unit weight as 2 gm/cc and moisture content of 25%. The head at which upward seepage will cause quick sand condition is in m.

1. 2.7
2. 1.9
3. 3.6
4. 1.1

Q. A sand deposit has a porosity of 0.375 and a specific gravity of 2.6, the critical hydraulic gradient for the sand deposit is

1. 2.975
2. 2.225
3. 1
4. 0.75

Q. A uniform collapsible sand stratum, 2.5 m thick. Has specific gravity of its sand as 2.65. With a natural void ratio of 0.65. The hydraulic head required to cause quick collapsible sand condition is

1. 2.50 m
2. 2.75 m
3. 3.25 m
4. 3.50 m

Q. Consider the following statements:
1. Quicksand is a special variety of sand.
2. Quicksand is not a material but a hydraulic condition.
3. In nature, quicksand condition is observed usually in coarse silt or fine sand.
Which of the above statements are correct?

1. 1, 2 and 3
2. 1 and 2 only
3. 2 and 3 only
4. 1 and 3 only

Q. An upward hydraulic gradient i of a certain magnitude will initiate the phenomenon of boiling in granular soils. The magnitude of this gradient is

1. $0\le i\le 0.5$
2. $0.5\le i\le 1.0$
3. $i\simeq 1.0$
4. $1<i\le 2$

Q. A sand deposit has a porosity of 1/3 and its specific gravity is 2.5. The critical hydraulic gradient to cause sand boiling in the stratum will be

1. 1.5
2. 1.25
3. 1.0
4. 0.75

Q. For a saturated sand deposit, the void ratio and the specific gravity of solids are 0.70 and 2.67 respectively. The critical (upward) hydraulic gradient for the deposit would be

1. 0.54
2. 0.98
3. 1.02
4. 1.87

Q. Which one of the following equations correctly gives the relationship between the specific gravity of soil grains ( G) and the hydraulic gradient (i) to initiate 'quick' condition in a sand having a void ratio of 0.5?

1. G = 0.5i + 1
2. G = i + 0.5
3. G = 1.5i + 1
4. G = 1.5i - 1

Q. In a soil specimen, the total stress, effective stress, hydraulic gradient and critical hydraulic gradient are $\sigma ,{\sigma }^{\prime },$ $i$ and $i_c$ respectively. For initiation of quick sand condition, which one of the following statement is TRUE?

1. ${\sigma }^{\prime }\ne 0andi=i_c$
2. $\sigma =0andi=i_c$
3. ${\sigma }^{\prime }\ne 0andi\ne i_c$
4. ${\sigma }^{\prime }=0andi=i_c$

Q. Statement (I): The possibility of quicksand condition occurring is more on the downstream of a weir on a permeable foundation than on the upstream end with an upward component of seepage velocity.
Statement {II): Seepage lines end with an upward component of seepage velocity at the downstream reaches of such a weir.

1. Both Statement (I) and Statement (II) are individually true and Statement (11) is the correct explanation of Statement (I)
2. Both Statement (I) and Statement (II) are individually true but Statement (II) is NOT the correct explanation of Statement (I)
3. Statement (I) is true but Statement (II) is false
4. Statement (I) is false but Statement (II) is true

Q. A 3 m thick soil starta has coefficient of permeability $4\times {10}^{-3}cm/secat{25}^{\circ }C$. A separate test gave porosity 30% and unit weight of 2.1 gm/cc at moisture content of 25%. If the temperature rises to ${40}^{\circ }C$, the increase in discharge per $c{m}^2$ to maintain critical condition is $3.92\times {10}^{-3}c{m}^3/sec/m^2$.
[ $\mu =10\times {10}^{-3}poise@{25}^{\circ }Cand6\times {10}^{-3}poise@{40}^{\circ }C$]

1. 2.62
2. 1.38
3. 4.60
4. 6.15