WorksheetsDAY 33 _PWD _permeability Seepage
Total questions: 15
Worksheet time: 10mins
The coefficient of permeability of soil primarily depends on:
A) Void ratio only
B) Grain size and viscosity of fluid
C) Degree of saturation
D) Specific gravity of solids
The flow net for seepage through an earth dam has 6 equipotential drops and 3 flow channels. If the head loss is 12 m,what is the seepage per meter length of dam is
if k=4×10−5 m/s?
(a)
A fully saturated clay layer is 6 m thick. The water table is at the surface. The saturated unit weight is 19 kN/m³. The effective stress at mid-depth is:
(a)
For isotropic homogeneous soil, the direction of seepage is:
A) Perpendicular to equipotential lines
B) Tangent to equipotential lines
C) Parallel to equipotential lines
D) Normal to flow lines
The ratio of permeability in horizontal direction to that in vertical direction for a stratified soil is generally:
1
<1
>1
0
A sand sample has a coefficient of permeability k=2×10−4 cm/s. If the hydraulic gradient is 0.5 and the cross-sectional area is 50 cm², compute the discharge for a head difference of 5 cm across a 50 cm sample.
(a)
In a constant head permeability test on a sand sample, doubling both the cross-sectional area and head difference will cause the discharge to:
A) Remain same
B) Double
C) Become four times
D) Halve
The ratio of seepage velocity to discharge velocity is equal to:
A) Porosity
B) Permeability
C) 1 / Porosity
D) Specific gravity
The phreatic line in an earthen dam represents:
A) Line of zero pore pressure
B) Line of zero effective stress
C) Boundary between saturated and unsaturated zones
D) Flow line
For a 2D flow net, if the head difference is halved and both NfN_fNf and NdN_dNd remain same, the seepage discharge will:
A) Remain same
B) Double
C) Reduce to half
D) Reduce to one-fourth
Match the following
Occurs when effective stress = 0
Quick sand condition
Tangent gives direction of seepage
Flow line
Constant head loss between two lines
Equipotential drop
Depends on specific gravity and void ratio
Critical hydraulic gradient
Inversely proportional to effective pore size
Capillary rise
The effective stress in soil increases when:
A) Water table rises
B) Pore pressure increases
C) Total stress increases but pore pressure remains constant
D) Both total and pore pressure increase equally
Assertion (A): The coefficient of permeability of clay is smaller than that of sand.
Reason (R): The voids in clay are very small and water flows through them under turbulent conditions.
A) Both A and R are true, and R is the correct explanation of A.
B) Both A and R are true, but R is not the correct explanation of A.
C) A is true, but R is false.
D) Both A and R are false
Assertion (A): In a properly constructed flow net, flow lines and equipotential lines intersect each other at right angles.
Reason (R): This orthogonality ensures that the potential drop between consecutive equipotential lines is constant throughout the flow field.
A) Both A and R are true, and R is the correct explanation of A.
B) Both A and R are true, but R is not the correct explanation of A.
C) A is true, but R is false.
D) Both A and R are false.
Assertion (A): The soil at the downstream end of a hydraulic structure may fail by piping if the exit gradient exceeds the critical gradient.
Reason (R): Piping occurs when the upward seepage pressure equals the submerged weight of soil, reducing effective stress to zero.
A) Both A and R are true, and R is the correct explanation of A.
B) Both A and R are true, but R is not the correct explanation of A.
C) A is true, but R is false.
D) A is false, but R is true.
