GEOTECHNICAL ENGINEERING 2026 – SOIL
MECHANICS, FOUNDATION DESIGN &
VERIFIED EXAM PRACTICE WITH DETAILED
RATIONALES
1. What does the term "void ratio" refer to in soil mechanics?
• A) The ratio of water to soil solids
• B) The ratio of air voids to total volume
• C) The ratio of volume of voids to volume of solids
• D) The ratio of pore water to pore air
✔ CORRECT ANSWER: C RATIONALE: Void ratio (e) = Vv/Vs. It describes how
much void space exists relative to the solid skeleton of the soil.
2. Which soil classification system uses the Plasticity Chart?
• A) AASHTO System
• B) Unified Soil Classification System (USCS)
• C) British Standard System
• D) FAO Soil Classification
✔ CORRECT ANSWER: B RATIONALE: The USCS uses the Casagrande plasticity
chart to classify fine-grained soils based on liquid limit and plasticity index.
3. The liquid limit of a soil is determined using:
• A) Proctor test
• B) Casagrande apparatus
• C) Hydrometer analysis
• D) Triaxial test
✔ CORRECT ANSWER: B RATIONALE: The liquid limit is the water content at which
soil transitions from plastic to liquid state, determined using the Casagrande cup device.
,4. Terzaghi's consolidation theory assumes:
• A) Soil is partially saturated
• B) Flow is horizontal
• C) Soil is fully saturated and flow is one-dimensional
• D) Soil has variable compressibility
✔ CORRECT ANSWER: C RATIONALE: Terzaghi's 1D consolidation theory assumes
full saturation, Darcy's law validity, constant permeability, and one-dimensional flow and
compression.
5. Which of the following best defines "effective stress"?
• A) Total stress minus cohesion
• B) Stress carried by pore water
• C) Total stress minus pore water pressure
• D) Stress at failure in shear
✔ CORRECT ANSWER: C RATIONALE: Effective stress (σ') = Total stress (σ) − Pore
water pressure (u). It governs soil strength and consolidation behavior.
6. Darcy's Law is expressed as:
• A) v = ki
• B) v = k/i
• C) v = i/k
• D) v = k + i
✔ CORRECT ANSWER: A RATIONALE: Darcy's Law states that flow velocity v = ki,
where k is the coefficient of permeability and i is the hydraulic gradient.
7. A soil with a uniformity coefficient (Cu) less than 4 is described as:
• A) Well-graded
, • B) Gap-graded
• C) Poorly graded (uniform)
• D) Broadly graded
✔ CORRECT ANSWER: C RATIONALE: Cu = D60/D10. A Cu < 4 (for gravels, Cu <
4; for sands, Cu < 6) indicates a poorly graded or uniformly graded soil.
8. In a Standard Proctor test, the compaction energy used is approximately:
• A) 2700 kJ/m³
• B) 600 kJ/m³
• C) 1500 kJ/m³
• D) 4500 kJ/m³
✔ CORRECT ANSWER: B RATIONALE: The Standard Proctor test applies
approximately 600 kJ/m³ of compaction energy. The Modified Proctor uses about 2700 kJ/m³.
9. The angle of internal friction (φ) of loose dry sand is approximately:
• A) 0°
• B) 10–15°
• C) 28–34°
• D) 45–50°
✔ CORRECT ANSWER: C RATIONALE: Loose dry sand typically has φ between 28°
and 34°. Dense sand can reach up to 45°, while cohesive soils may have φ ≈ 0° (undrained).
10. Which test directly measures undrained shear strength in the field?
• A) Standard Penetration Test (SPT)
• B) Vane Shear Test
• C) Cone Penetration Test (CPT)
• D) Plate Load Test
, ✔ CORRECT ANSWER: B RATIONALE: The field vane shear test directly measures
undrained shear strength (Su) of soft cohesive soils by rotating a vane and recording torque at
failure.
11. Rankine's passive earth pressure coefficient (Kp) for φ = 30° is:
• A) 1.0
• B) 2.0
• C) 3.0
• D) 4.0
✔ CORRECT ANSWER: C RATIONALE: Kp = tan²(45 + φ/2) = tan²(60°) = 3.0 for φ =
30°. Passive pressure acts when the wall moves toward the soil.
12. What is the primary cause of secondary consolidation?
• A) Drainage of excess pore water
• B) Increase in effective stress
• C) Creep of the soil skeleton
• D) Swelling due to unloading
✔ CORRECT ANSWER: C RATIONALE: Secondary consolidation (creep) occurs after
excess pore water pressure has dissipated, due to the viscous deformation of the soil skeleton
over time.
13. The plasticity index (PI) is defined as:
• A) PI = PL − LL
• B) PI = LL − PL
• C) PI = LL + PL
• D) PI = LL × PL
✔ CORRECT ANSWER: B RATIONALE: Plasticity Index = Liquid Limit − Plastic
Limit. It indicates the range of water content over which the soil behaves plastically.
MECHANICS, FOUNDATION DESIGN &
VERIFIED EXAM PRACTICE WITH DETAILED
RATIONALES
1. What does the term "void ratio" refer to in soil mechanics?
• A) The ratio of water to soil solids
• B) The ratio of air voids to total volume
• C) The ratio of volume of voids to volume of solids
• D) The ratio of pore water to pore air
✔ CORRECT ANSWER: C RATIONALE: Void ratio (e) = Vv/Vs. It describes how
much void space exists relative to the solid skeleton of the soil.
2. Which soil classification system uses the Plasticity Chart?
• A) AASHTO System
• B) Unified Soil Classification System (USCS)
• C) British Standard System
• D) FAO Soil Classification
✔ CORRECT ANSWER: B RATIONALE: The USCS uses the Casagrande plasticity
chart to classify fine-grained soils based on liquid limit and plasticity index.
3. The liquid limit of a soil is determined using:
• A) Proctor test
• B) Casagrande apparatus
• C) Hydrometer analysis
• D) Triaxial test
✔ CORRECT ANSWER: B RATIONALE: The liquid limit is the water content at which
soil transitions from plastic to liquid state, determined using the Casagrande cup device.
,4. Terzaghi's consolidation theory assumes:
• A) Soil is partially saturated
• B) Flow is horizontal
• C) Soil is fully saturated and flow is one-dimensional
• D) Soil has variable compressibility
✔ CORRECT ANSWER: C RATIONALE: Terzaghi's 1D consolidation theory assumes
full saturation, Darcy's law validity, constant permeability, and one-dimensional flow and
compression.
5. Which of the following best defines "effective stress"?
• A) Total stress minus cohesion
• B) Stress carried by pore water
• C) Total stress minus pore water pressure
• D) Stress at failure in shear
✔ CORRECT ANSWER: C RATIONALE: Effective stress (σ') = Total stress (σ) − Pore
water pressure (u). It governs soil strength and consolidation behavior.
6. Darcy's Law is expressed as:
• A) v = ki
• B) v = k/i
• C) v = i/k
• D) v = k + i
✔ CORRECT ANSWER: A RATIONALE: Darcy's Law states that flow velocity v = ki,
where k is the coefficient of permeability and i is the hydraulic gradient.
7. A soil with a uniformity coefficient (Cu) less than 4 is described as:
• A) Well-graded
, • B) Gap-graded
• C) Poorly graded (uniform)
• D) Broadly graded
✔ CORRECT ANSWER: C RATIONALE: Cu = D60/D10. A Cu < 4 (for gravels, Cu <
4; for sands, Cu < 6) indicates a poorly graded or uniformly graded soil.
8. In a Standard Proctor test, the compaction energy used is approximately:
• A) 2700 kJ/m³
• B) 600 kJ/m³
• C) 1500 kJ/m³
• D) 4500 kJ/m³
✔ CORRECT ANSWER: B RATIONALE: The Standard Proctor test applies
approximately 600 kJ/m³ of compaction energy. The Modified Proctor uses about 2700 kJ/m³.
9. The angle of internal friction (φ) of loose dry sand is approximately:
• A) 0°
• B) 10–15°
• C) 28–34°
• D) 45–50°
✔ CORRECT ANSWER: C RATIONALE: Loose dry sand typically has φ between 28°
and 34°. Dense sand can reach up to 45°, while cohesive soils may have φ ≈ 0° (undrained).
10. Which test directly measures undrained shear strength in the field?
• A) Standard Penetration Test (SPT)
• B) Vane Shear Test
• C) Cone Penetration Test (CPT)
• D) Plate Load Test
, ✔ CORRECT ANSWER: B RATIONALE: The field vane shear test directly measures
undrained shear strength (Su) of soft cohesive soils by rotating a vane and recording torque at
failure.
11. Rankine's passive earth pressure coefficient (Kp) for φ = 30° is:
• A) 1.0
• B) 2.0
• C) 3.0
• D) 4.0
✔ CORRECT ANSWER: C RATIONALE: Kp = tan²(45 + φ/2) = tan²(60°) = 3.0 for φ =
30°. Passive pressure acts when the wall moves toward the soil.
12. What is the primary cause of secondary consolidation?
• A) Drainage of excess pore water
• B) Increase in effective stress
• C) Creep of the soil skeleton
• D) Swelling due to unloading
✔ CORRECT ANSWER: C RATIONALE: Secondary consolidation (creep) occurs after
excess pore water pressure has dissipated, due to the viscous deformation of the soil skeleton
over time.
13. The plasticity index (PI) is defined as:
• A) PI = PL − LL
• B) PI = LL − PL
• C) PI = LL + PL
• D) PI = LL × PL
✔ CORRECT ANSWER: B RATIONALE: Plasticity Index = Liquid Limit − Plastic
Limit. It indicates the range of water content over which the soil behaves plastically.
