50 Geotechnical Engineering Questions for APSC AE Exam
50 Geotechnical Engineering Questions for APSC Assistant Engineer Exam
1. What is the primary source of soil in geotechnical engineering?
a) Chemical decomposition
b) Weathering of rocks
c) Organic deposition
d) Industrial waste
b) Weathering of rocks
Soil is primarily formed by the weathering of rocks, which includes physical (mechanical) and chemical processes that break down rocks into smaller particles over time.
2. Which soil type has the smallest particle size?
a) Sand
b) Silt
c) Clay
d) Gravel
c) Clay
Clay has the smallest particle size, typically less than 0.002 mm, compared to silt (0.002–0.075 mm), sand (0.075–4.75 mm), and gravel (>4.75 mm).
3. Darcy’s law is applicable for which type of flow?
a) Turbulent flow
b) Laminar flow
c) Transitional flow
d) Non-linear flow
b) Laminar flow
Darcy’s law (q = kiA) applies to laminar flow through porous media like soil, where the flow is steady and proportional to the hydraulic gradient.
4. What is the unit weight of water at 4°C?
a) 9.81 kN/m³
b) 10 kN/m³
c) 8.9 kN/m³
d) 12 kN/m³
a) 9.81 kN/m³
The unit weight of water at 4°C is 9.81 kN/m³, derived from its density (1000 kg/m³) multiplied by gravitational acceleration (9.81 m/s²).
5. Which test is used to determine the shear strength of soil?
a) Proctor test
b) Triaxial test
c) Hydrometer test
d) Sieve analysis
b) Triaxial test
The triaxial test measures shear strength parameters (cohesion and angle of internal friction) by subjecting a soil sample to controlled stresses under confined conditions.
6. What is the primary cause of consolidation in clayey soils?
a) Evaporation
b) Expulsion of water
c) Chemical reaction
d) Particle rearrangement
b) Expulsion of water
Consolidation in clayey soils occurs due to the gradual expulsion of water from voids under sustained loading, reducing soil volume over time.
7. The coefficient of permeability of sand is typically in the range of:
a) 10⁻⁷ to 10⁻⁵ cm/s
b) 10⁻³ to 10⁻¹ cm/s
c) 10⁻¹⁰ to 10⁻⁸ cm/s
d) 10⁻¹² to 10⁻¹⁰ cm/s
b) 10⁻³ to 10⁻¹ cm/s
Sand has relatively high permeability due to larger particle sizes, allowing water to flow easily, typically in the range of 10⁻³ to 10⁻¹ cm/s.
8. What is the angle of internal friction for loose sand?
a) 15°–20°
b) 25°–30°
c) 35°–40°
d) 45°–50°
b) 25°–30°
Loose sand has a lower angle of internal friction, typically 25°–30°, reflecting its reduced shear resistance compared to dense sand (35°–40°).
9. Which foundation is suitable for black cotton soil?
a) Spread footing
b) Pile foundation
c) Raft foundation
d) Strip footing
b) Pile foundation
Black cotton soil is expansive, so pile foundations are preferred as they transfer loads to deeper, stable layers, avoiding settlement issues.
10. The bearing capacity of soil is primarily influenced by:
a) Soil color
b) Shear strength
c) Particle size
d) Organic content
b) Shear strength
Bearing capacity depends on shear strength (cohesion and friction), which determines the soil’s ability to resist failure under load.
11. Evaluate the following statement: ‘The void ratio of a soil can be greater than 1.’
a) True
b) False
a) True
The void ratio (e = V_v/V_s) can exceed 1 in loose soils like clay or peat, where the volume of voids is greater than the volume of solids.
12. Which of the following statements is correct about Darcy’s law?
a) It applies only to turbulent flow.
b) It relates discharge velocity to hydraulic gradient.
c) It is used to measure soil shear strength.
d) It determines soil compressibility.
b) It relates discharge velocity to hydraulic gradient.
Darcy’s law (v = ki) states that the discharge velocity of water through soil is proportional to the hydraulic gradient and permeability coefficient.
13. Evaluate the following statement: ‘Cohesion is zero for pure sand.’
a) True
b) False
a) True
Pure sand is cohesionless, relying solely on frictional resistance (angle of internal friction) for shear strength, unlike cohesive soils like clay.
14. Which statement is true about consolidation?
a) It occurs instantaneously in all soils.
b) It is significant in cohesive soils like clay.
c) It increases soil permeability.
d) It is unrelated to pore water pressure.
b) It is significant in cohesive soils like clay.
Consolidation is a time-dependent process in cohesive soils like clay, where water is expelled from voids, causing volume reduction under load.
15. Evaluate the following statement: ‘The liquid limit is the water content at which soil behaves like a liquid.’
a) True
b) False
a) True
The liquid limit is the water content at which soil transitions from plastic to liquid behavior, determined using Casagrande’s apparatus.
16. Which of the following statements is correct about SPT?
a) It measures soil permeability.
b) It is conducted in the laboratory.
c) It provides an N-value indicating soil density.
d) It is used for chemical analysis of soil.
c) It provides an N-value indicating soil density.
The Standard Penetration Test (SPT) is an in-situ test that measures the N-value (blows per 30 cm), indicating soil density and strength.
17. Evaluate the following statement: ‘Negative skin friction occurs in piles when the surrounding soil settles.’
a) True
b) False
a) True
Negative skin friction occurs when settling soil drags down a pile, increasing the load on it, typically in compressible clays.
18. Which statement is true about bearing capacity?
a) It is independent of soil shear strength.
b) It increases with foundation depth.
c) It is unaffected by groundwater.
d) It is constant for all soil types.
b) It increases with foundation depth.
Bearing capacity increases with depth due to increased overburden pressure, which enhances soil shear strength (per Terzaghi’s theory).
19. Evaluate the following statement: ‘Well-graded soil has a wide range of particle sizes.’
a) True
b) False
a) True
Well-graded soil contains a wide range of particle sizes, improving its compaction and strength, as opposed to poorly graded soil.
20. Which of the following statements is correct about soil compaction?
a) It increases air voids.
b) It is achieved at optimum moisture content.
c) It reduces soil strength.
d) It is only applicable to clay soils.
b) It is achieved at optimum moisture content.
Compaction maximizes soil density at the optimum moisture content (per Proctor test), reducing air voids and increasing strength.
21. Calculate the void ratio of a soil sample with a porosity of 40%.
a) 0.67
b) 0.40
c) 1.50
d) 0.25
a) 0.67
Porosity (n) = V_v/V, void ratio (e) = V_v/V_s = n/(1-n). Given n = 0.4, e = 0.4/(1-0.4) = 0.4/0.6 = 0.67.
22. A soil sample has a dry unit weight of 16 kN/m³ and a specific gravity of 2.65. If the void ratio is 0.6, calculate the degree of saturation (%).
a) 50%
b) 62.5%
c) 75%
d) 100%
b) 62.5%
Using γ_d = Gγ_w/(1+e), γ_w = 9.81 kN/m³, γ_d = 16, e = 0.6, G = 2.65. Degree of saturation S = (γ_d(1+e) - Gγ_w)/(eγ_w). Calculate: γ_d(1+e) = 16 × 1.6 = 25.6, Gγ_w = 2.65 × 9.81 = 26, S = (25.6 - 26)/(0.6 × 9.81) = -0.4/5.886 = 0.625 or 62.5%.
23. A square footing of 2 m × 2 m carries a load of 800 kN. Calculate the average bearing pressure (kPa).
24. A soil layer has a permeability of 10⁻³ cm/s and a hydraulic gradient of 0.5. Calculate the seepage velocity (cm/s) if the porosity is 0.4.
a) 8.33 × 10⁻⁴
b) 1.25 × 10⁻³
c) 2.5 × 10⁻³
d) 5.0 × 10⁻³
b) 1.25 × 10⁻³
Seepage velocity (v_s) = ki/n, where k = 10⁻³ cm/s, i = 0.5, n = 0.4. v_s = (10⁻³ × 0.5)/0.4 = 0.0005/0.4 = 1.25 × 10⁻³ cm/s.
25. A clay layer 4 m thick has a coefficient of consolidation of 0.02 cm²/s. Calculate the time (days) for 50% consolidation if the drainage is one-way.
a) 46.3 days
b) 92.6 days
c) 138.9 days
d) 185.2 days
b) 92.6 days
For 50% consolidation, T_v = 0.197. Time t = T_v H²/C_v. H = 4 m (drainage path), C_v = 0.02 cm²/s = 1.728 m²/day (0.02 × 86400/10000). t = 0.197 × 4² / 1.728 = 3.152/1.728 = 92.6 days.
26. Calculate the effective stress (kPa) at a depth of 5 m in a soil with a unit weight of 18 kN/m³ and a water table at 2 m depth. Assume γ_w = 9.81 kN/m³.
31. What is the standard size of the plate in a plate load test?
a) 30 cm
b) 60 cm
c) 75 cm
d) 100 cm
c) 75 cm
The standard plate size for a plate load test is 75 cm (diameter or side), used to determine the bearing capacity and settlement of soil in-situ.
32. What does SPT stand for in geotechnical engineering?
a) Soil Penetration Test
b) Standard Penetration Test
c) Static Pressure Test
d) Shear Plate Test
b) Standard Penetration Test
SPT stands for Standard Penetration Test, a widely used in-situ test to assess soil density and strength by counting blows to drive a sampler.
33. The liquid limit of a soil is determined using:
a) Casagrande’s apparatus
b) Hydrometer
c) Pycnometer
d) Proctor needle
a) Casagrande’s apparatus
The liquid limit is measured using Casagrande’s apparatus, which determines the water content at which a soil groove closes after 25 blows.
34. Which soil is most susceptible to liquefaction?
a) Dense sand
b) Loose saturated sand
c) Clay
d) Gravel
b) Loose saturated sand
Loose saturated sand is prone to liquefaction during earthquakes, as cyclic loading causes a loss of shear strength due to increased pore pressure.
35. The compaction of soil is achieved by:
a) Adding water
b) Reducing air voids
c) Increasing pore pressure
d) Chemical stabilization
b) Reducing air voids
Compaction reduces air voids in soil by mechanical means, increasing density and strength, typically at the optimum moisture content.
36. What is the purpose of a geotechnical investigation?
a) To determine soil properties
b) To measure rainfall
c) To analyze air quality
d) To study vegetation
a) To determine soil properties
Geotechnical investigations assess soil properties (e.g., strength, compressibility) to guide foundation design and ensure structural stability.
37. The factor of safety for slope stability is typically:
a) 0.5–1.0
b) 1.2–1.5
c) 2.0–2.5
d) 3.0–4.0
b) 1.2–1.5
A factor of safety of 1.2–1.5 is typical for slope stability, balancing safety and economy in design against sliding failure.
38. What is the typical depth of a shallow foundation?
a) Less than 3 m
b) 3–10 m
c) 10–20 m
d) More than 20 m
a) Less than 3 m
Shallow foundations, like footings or rafts, are typically placed at depths less than 3 m, where soil has adequate bearing capacity.
39. The Proctor test is used to determine:
a) Shear strength
b) Optimum moisture content
c) Permeability
d) Grain size
b) Optimum moisture content
The Proctor test determines the optimum moisture content and maximum dry density for soil compaction, critical for construction projects.
40. Which method is used to analyze slope stability?
a) Bishop’s method
b) Terzaghi’s method
c) Darcy’s method
d) Proctor’s method
a) Bishop’s method
Bishop’s method is a widely used limit equilibrium method to analyze slope stability, considering circular failure surfaces and interslice forces.
41. The plasticity index is the difference between:
a) Liquid limit and plastic limit
b) Plastic limit and shrinkage limit
c) Liquid limit and shrinkage limit
d) Dry density and wet density
a) Liquid limit and plastic limit
The plasticity index (PI) = LL - PL, indicating the range of water content where soil remains plastic, a key property for clayey soils.
42. Which equipment is used for in-situ density determination?
a) Sand cone apparatus
b) Hydrometer
c) Pycnometer
d) Casagrande’s device
a) Sand cone apparatus
The sand cone apparatus measures in-situ soil density by replacing excavated soil with sand of known density, used in compaction control.
43. The ultimate bearing capacity of soil is calculated using:
a) Terzaghi’s theory
b) Darcy’s law
c) Stokes’ law
d) Mohr’s theory
a) Terzaghi’s theory
Terzaghi’s bearing capacity theory calculates the ultimate bearing capacity using soil shear strength parameters and foundation dimensions.
44. Which type of roller is best for compacting cohesive soils?
a) Smooth wheel roller
b) Pneumatic roller
c) Sheepsfoot roller
d) Vibratory roller
c) Sheepsfoot roller
Sheepsfoot rollers are ideal for cohesive soils like clay, as their protrusions knead the soil, improving compaction by breaking down lumps.
45. The active earth pressure is calculated using:
a) Rankine’s theory
b) Stokes’ law
c) Darcy’s law
d) Terzaghi’s equation
a) Rankine’s theory
Rankine’s theory calculates active earth pressure behind retaining walls, assuming a conjugate failure plane based on soil friction angle.
46. The settlement of a foundation is primarily due to:
a) Compaction
b) Consolidation
c) Liquefaction
d) Erosion
b) Consolidation
Foundation settlement is primarily due to consolidation, where soil compresses over time under load, especially in clays, causing volume reduction.
47. Which test is used to classify fine-grained soils?
a) Sieve analysis
b) Atterberg limits
c) Proctor test
d) Core cutter method
b) Atterberg limits
Atterberg limits (liquid limit, plastic limit, shrinkage limit) classify fine-grained soils based on their behavior at different water contents.
48. The permeability of soil is measured in:
a) cm/s
b) kN/m²
c) kg/m³
d) m²
a) cm/s
Permeability (coefficient of permeability, k) is measured in cm/s, representing the velocity of water flow through soil under a unit hydraulic gradient.
49. The term ‘effective stress’ in soil refers to:
a) Total stress minus pore water pressure
b) Total stress plus pore water pressure
c) Shear stress only
d) Compressive stress only
a) Total stress minus pore water pressure
Effective stress (σ') = Total stress (σ) - Pore water pressure (u), governing soil strength and deformation behavior.
50. The factor of safety for bearing capacity is usually:
a) 1.0
b) 2.0–3.0
c) 4.0–5.0
d) 6.0–7.0
b) 2.0–3.0
A factor of safety of 2.0–3.0 is typically used for bearing capacity to ensure foundations are safe against shear failure and excessive settlement.
