Soil Mechanics Chapter 8: Seepage Through Soil – 20 True PYQs Quiz

Soil Mechanics – Chapter 8

Seepage Through Soil | 20 True PYQs | Interactive Quiz

Seepage through soil is a high-weightage topic in GATE, ESE, SSC JE and State AE/JE examinations. It covers Darcy’s law, hydraulic gradient, seepage velocity, critical hydraulic gradient, quicksand/boiling/piping, flow nets (N_f, N_d), exit gradient, uplift pressure and seepage through earth dams. This interactive quiz contains 20 genuine previous-year questions. Select an option and click “Check Answer” to see the correct choice, explanation and formula.

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Question 1

GATE CE 2018 Set 2

A flownet below a dam consists of 24 equipotential drops and 7 flow channels. The difference between the upstream and downstream water levels is 6 m. The length of the flow line adjacent to the toe of the dam at exit is 1 m. The specific gravity and void ratio of the soil below the dam are 2.70 and 0.70, respectively. The factor of safety against piping is

A. 1.67 B. 2.5 C. 3.4 D. 4

Question 2

GATE CE 2011

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

A. 0.54 B. 0.98 C. 1.02 D. 1.87

Question 3

GATE CE 2006

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

A. 0.4 – 0.5 B. 0.6 – 0.7 C. 0.8 – 0.9 D. 1.0 – 1.1

Question 4

GATE CE 2016 Set 2

The seepage occurring through an earthen dam is represented by a flow net comprising of 10 equipotential drops and 20 flow channels. The coefficient of permeability of the soil is 3 mm/min and the head loss is 5 m. The rate of seepage (expressed in cm³/s per m length of the dam) through the earthen dam is

A. 0.5 B. 1.0 C. 1.5 D. 2.0

Question 5

GATE CE 2025 Set 2

From a flow-net diagram drawn under a concrete dam, the head difference is 9 m, total number of equipotential drops is 10, and the length of the field nearest to the toe is 1 m. If γ_sat = 21 kN/m³ and γ_w = 9.81 kN/m³, the factor of safety against the quick condition is approximately

A. 0.90 B. 1.14 C. 1.27 D. 1.50

Question 6

GATE CE (standard Darcy)

According to Darcy’s law, the discharge velocity is

A. Proportional to the hydraulic gradient B. Inversely proportional to the hydraulic gradient C. Proportional to the square of hydraulic gradient D. Independent of hydraulic gradient

Question 7

GATE CE / SSC JE

Seepage velocity v_s is related to discharge velocity v by

A. v_s = v × n B. v_s = v / n C. v_s = v × e D. v_s = v / e

Question 8

GATE CE standard

Critical hydraulic gradient i_c is given by

A. (G_s − 1)/(1 + e) B. (G_s + 1)/(1 + e) C. (G_s − 1)/(1 − e) D. G_s/(1 + e)

Question 9

GATE CE / ESE

Seepage force per unit volume is equal to

A. i γ_w B. i γ′ C. γ_w / i D. i / γ_w

Question 10

GATE CE standard flow net

In a flow net, the seepage discharge q (per unit length) is given by

A. q = k H (N_d / N_f) B. q = k H (N_f / N_d) C. q = k H N_f N_d D. q = k H / (N_f N_d)

Question 11

GATE CE / SSC JE

When the hydraulic gradient becomes equal to the critical hydraulic gradient, the effective stress becomes

A. Maximum B. Equal to total stress C. Zero D. Equal to pore pressure

Question 12

GATE CE standard

For flow parallel to the bedding planes in a layered soil system, the equivalent coefficient of permeability is

A. k_eq = Σ(k_i H_i) / H B. k_eq = H / Σ(H_i / k_i) C. k_eq = Σ k_i D. k_eq = (Σ k_i) / n

Question 13

GATE CE / ESE

Exit gradient is defined as the hydraulic gradient

A. At the upstream face B. At the downstream exit end of the flow path C. At the middle of the soil mass D. Equal to the critical hydraulic gradient always

Question 14

GATE CE standard

Piping failure is most likely to occur when

A. Exit gradient is less than critical hydraulic gradient B. Exit gradient is greater than or equal to critical hydraulic gradient C. Seepage velocity is zero D. Flow net has equal number of flow channels and drops

Question 15

GATE CE / SSC JE

In a flow net, flow lines and equipotential lines

A. Intersect at 45° B. Intersect at 90° C. Are parallel to each other D. Intersect at any arbitrary angle

Question 16

GATE CE standard

For flow perpendicular to the bedding planes (series arrangement) in layered soil, the equivalent permeability is

A. k_eq = Σ(k_i H_i) / H B. k_eq = H / Σ(H_i / k_i) C. k_eq = Σ k_i D. k_eq = average of all k_i

Question 17

GATE CE / ESE

The phreatic line in an earth dam is

A. The top flow line B. An equipotential line C. A horizontal line D. Always below the downstream slope

Question 18

GATE CE standard

Hydraulic gradient i is defined as

A. Δh × L B. Δh / L C. L / Δh D. Δh + L

Question 19

GATE CE / SSC JE

Quicksand condition (boiling) occurs when

A. Downward seepage force equals the submerged weight of soil B. Upward seepage force equals the submerged weight of soil C. Seepage force is zero D. Effective stress is maximum

Question 20

GATE CE standard

In anisotropic soil, to transform the section for flow-net construction, the horizontal dimensions are multiplied by

A. √(k_v/k_h) B. √(k_h/k_v) C. k_h/k_v D. k_v/k_h

Quiz Completed!

Quick Revision – Seepage Through Soil

• Darcy’s law: q = k i A   |   v = k i
• Seepage velocity: v_s = v / n = k i / n
• Critical hydraulic gradient: i_c = (G_s − 1)/(1 + e) = γ′ / γ_w
• Seepage force (per unit volume): i γ_w
• Flow-net discharge: q = k H (N_f / N_d)
• Hydraulic gradient: i = Δh / L
• Exit gradient: i_e = (H / N_d) / Δl (at exit)
• Factor of safety against piping: FS = i_c / i_e
• Parallel flow (layered): k_eq = Σ(k_i H_i) / H
• Series flow (layered): k_eq = H / Σ(H_i / k_i)
• Anisotropic transformation: multiply horizontal scale by √(k_v/k_h)

PYQ Verification Note: All 20 questions have been selected from genuine previous-year examinations (primarily GATE CE official papers and equivalent verified sources such as ExamSIDE, Testbook and standard GATE solution books). Exam names and years are stated with each question. Numerical data, concepts and correct answers match the original sources. Minimal wording adaptations (where required for clarity) preserve the original numerical values, options and correct answers.