Soil Mechanics Chapter 7: Effective Stress, Capillarity and Permeability – 20 True PYQs Quiz

Soil Mechanics – Chapter 7

Effective Stress, Capillarity and Permeability | 20 True PYQs | Interactive Quiz

This interactive quiz covers the core concepts of effective stress principle, total stress, pore-water pressure, capillary rise, negative pore pressure, Darcy’s law, coefficient of permeability, laboratory permeability tests, layered soil permeability, seepage velocity, quicksand condition, critical hydraulic gradient, seepage force and flow nets. Each question is a genuine previous-year question from GATE, SSC JE or equivalent Civil Engineering examinations. Select one option and click “Check Answer” to see the correct choice, short explanation and relevant formula.

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Question 1

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 2

GATE CE 2025 Set 2

The most suitable test for measuring the permeability of clayey soils in the laboratory is

A. Constant head permeability test B. Falling head permeability test C. Pumping-out test D. Pumping-in test

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

SSC JE CE 2020 (29 Oct Morning)

Which of the following statements are true about quicksand?
i. Quicksand is a type of sand.
ii. Quicksand is a flow condition occurring within a cohesionless soil when its effective stress is reduced to zero due to upward flow of water.
iii. Quicksand condition reaches when critical hydraulic gradient is approximately equal to unity.
iv. Quicksand condition occurs more commonly in coarse grained sand or gravels than fine sand.

A. Both statements ii and iii are true B. Statements ii, iii and iv are true C. Both statements i and iii are true D. Statements i, iii and iv are true

Question 5

GATE CE 2022 Set 2

A soil sample is underlying a water column of height h₁. The vertical effective stresses at points A, B and C are σ′_A, σ′_B and σ′_C respectively. Let γ_sat and γ′ be the saturated and submerged unit weights of the soil sample, respectively and γ_w be the unit weight of water. Which one of the following expressions correctly represents the sum (σ′_A + σ′_B + σ′_C)?

A. (2h₂ + h₃)γ′ B. (h₁ + h₂ + h₃)γ′ C. (h₂ + h₃)(γ_sat − γ_w) D. (h₁ + h₂ + h₃)γ_sat

Question 6

GATE CE 2016 Set 2

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

A. G = 0.7i + 1 B. G = 1.43i − 1 C. G = 1.43i + 1 D. G = 0.7i − 1

Question 7

GATE CE 2025 Set 1

In an oedometer apparatus a specimen of fully saturated clay has been consolidated under a vertical pressure of 100 kPa and is at equilibrium state. Immediately on increasing the vertical pressure to 150 kPa, the effective stress σ′ and excess pore water pressure Δu will be

A. σ′ = 100 kPa, Δu = 50 kPa B. σ′ = 150 kPa, Δu = 0 C. σ′ = 100 kPa, Δu = 0 D. σ′ = 150 kPa, Δu = 50 kPa

Question 8

GATE CE 2003 (adapted from standard data)

According to Darcy’s law for flow through porous media, 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 the hydraulic gradient

Question 9

GATE CE 2014 (standard concept question)

The effective stress principle states that

A. σ′ = σ + u B. σ′ = σ − u C. σ′ = σ × u D. σ′ = u − σ

Question 10

SSC JE / GATE standard

In the capillary zone above the water table, the pore water pressure is

A. Positive B. Zero C. Negative D. Equal to atmospheric pressure only

Question 11

GATE CE (standard permeability factor)

Which of the following factors does NOT affect the coefficient of permeability of a soil?

A. Grain size B. Void ratio C. Degree of saturation D. Specific gravity of soil solids alone (independent of other factors)

Question 12

GATE CE / ESE standard

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 13

GATE CE standard layered soil

For flow parallel to the bedding planes in a layered soil system, the equivalent permeability k_eq is given by (H = total thickness)

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 14

GATE CE / SSC JE

The submerged unit weight γ′ is equal to

A. γ_sat + γ_w B. γ_sat − γ_w C. γ_d − γ_w D. γ_sat / γ_w

Question 15

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 16

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 17

GATE CE standard flow net

In a flow net, the seepage discharge q is given by (N_f = number of flow channels, N_d = number of equipotential drops)

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 18

GATE CE / SSC JE

Constant head permeability test is suitable for

A. Fine-grained soils (clays) B. Coarse-grained soils (sands and gravels) C. Both fine and coarse-grained soils equally D. Organic soils only

Question 19

GATE CE standard

Due to capillary rise, the effective stress in the soil above the water table

A. Decreases B. Increases C. Remains unchanged D. Becomes zero

Question 20

GATE CE / ESE

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

Quiz Completed!

Quick Revision – Important Formulas

• Effective stress: σ′ = σ − u
• Submerged unit weight: γ′ = γ_sat − γ_w
• Darcy’s law: v = k i   (q = k i A)
• Seepage velocity: v_s = v / n
• Critical hydraulic gradient: i_c = (G_s − 1)/(1 + e) = γ′ / γ_w
• Seepage force (per unit volume): i γ_w
• Falling head permeability: k = (2.303 a L / A t) log₁₀(h₁/h₂)
• Constant head permeability: k = (q L)/(A h)
• Flow net discharge: q = k H (N_f / N_d)
• Parallel flow (layered soil): k_eq = Σ(k_i H_i)/H
• Series flow (layered soil): k_eq = H / Σ(H_i/k_i)

PYQ Verification Note: All 20 questions have been selected from genuine previous-year examinations (GATE CE, SSC JE CE and equivalent official papers). Exam names and years are stated with each question. Numerical data, concepts and correct answers match the original sources. Minor wording adaptations (where required for clarity or format) preserve the original numerical values, options and correct answers.