CIV 418: GEOTECHNICAL
ENGINEERING
Final Examination Questions & Answers with Verified Solutions
2026/2027
Course: CIV 418 — Geotechnical Engineering
Total Questions: 60 Multiple-Choice Questions
Instructions: Choose the single best answer for each question. Correct answers and
detailed explanations are highlighted in green for effective study and review.
1. The phase relationship defining soil void ratio (e) is given by the ratio of the volume of
voids to the:
A. Total volume of soil mass
B. Volume of solid soil grains
C. Volume of water present in voids
D. Mass of dry solid particles
Rationale: Void ratio e is strictly defined as e = V_v / V_s, whereas porosity n is defined as V_v / V_t.
2. According to the Unified Soil Classification System (USCS), a fine-grained soil is
classified as a clay or silt based on its position relative to the 'A-line' on the Plasticity
Chart. The equation for the 'A-line' is:
A. PI = 0.73 * (LL - 20)
B. PI = 0.50 * (LL - 10)
C. PI = 0.90 * (LL - 30)
D. PI = 0.73 * (LL - 50)
Rationale: The USCS plasticity chart uses PI = 0.73(LL - 20) to separate inorganic clays (above the line)
from inorganic silts and organic soils (below the line).
3. Darcy's Law for one-dimensional fluid flow through porous soil media assumes that
flow velocity is directly proportional to the hydraulic gradient. This relationship holds
true strictly under:
, A. Turbulent flow conditions in coarse gravels
B. Laminar flow conditions in saturated soils
C. Unsaturated soils with variable air volume
D. High-velocity pipeline fluid dynamics
Rationale: Darcy's law v = k*i applies only when flow through pore channels is laminar (low Reynolds
numbers), typical of most saturated sands, silts, and clays.
4. Terzaghi's Principle of Effective Stress states that the effective vertical stress (σ')
acting on a soil skeleton equals total stress (σ) minus:
A. Hydraulic gradient pressure
B. Pore water pressure (u)
C. Overburden bulk density
D. Lateral earth pressure coefficient
Rationale: Effective stress controls soil strength and volume change, defined by Terzaghi's equation σ' =
σ - u.
5. Quick Condition (or quicksand condition) in cohesionless granular soils occurs when
the upward hydraulic gradient reaches the critical hydraulic gradient (i_cr), which
causes:
A. Effective stress to drop to zero, completely destroying shear strength
B. Total stress to double in magnitude
C. Permeability to fall to zero
D. Soil dry density to reach maximum index value
Rationale: When upward seepage drag balances submerged unit weight, u = σ, causing σ' = 0 and
reducing shear strength in cohesionless soils (τ = σ' tan φ) to zero.
6. In Terzaghi's 1-D Consolidation theory, the Time Factor (T_v) is mathematically
expressed as:
A. T_v = (c_v * H_d^2) / t
B. T_v = (c_v * t) / H_d^2
C. T_v = (k * t) / (m_v * γ_w)
D. T_v = (t * H_d) / c_v
Rationale: The dimensionless time factor T_v relates consolidation coefficient c_v, elapsed time t, and
, drainage path length H_d via T_v = c_v * t / H_d^2.
7. A clay soil layer is subjected to double drainage conditions. If the total thickness of the
clay layer is 6 meters, the maximum length of the drainage path (H_d) is:
A. 6.0 meters
B. 3.0 meters
C. 1.5 meters
D. 12.0 meters
Rationale: With double drainage (top and bottom pervious boundaries), water escapes from both sides,
so H_d is half the total layer thickness: 6 m / 2 = 3 m.
8. Overconsolidation Ratio (OCR) of a soil deposit is defined as the ratio of:
A. Preconsolidation stress (σ'_p) to current effective vertical stress (σ'_v0)
B. Current effective stress to initial pore pressure
C. Total stress to effective stress
D. Unconfined compressive strength to remolded strength
Rationale: OCR = σ'_p / σ'_v0. An OCR > 1 indicates the soil experienced higher vertical effective
stresses in its geological history than at present.
9. The standard Mohr-Coulomb shear strength criterion defines shear strength (τ) of a
soil as a function of effective normal stress (σ') by:
A. τ = c' + σ' sin φ'
B. τ = c' + σ' tan φ'
C. τ = c' + σ' cos φ'
D. τ = σ' / tan φ'
Rationale: Mohr-Coulomb models shear resistance as a combination of effective cohesion intercept c' and
frictional resistance σ' tan φ'.
10. In a standard Consolidated-Undrained (CU) triaxial shear test on saturated clay, pore
water pressure is measured to determine:
A. The total friction angle only
ENGINEERING
Final Examination Questions & Answers with Verified Solutions
2026/2027
Course: CIV 418 — Geotechnical Engineering
Total Questions: 60 Multiple-Choice Questions
Instructions: Choose the single best answer for each question. Correct answers and
detailed explanations are highlighted in green for effective study and review.
1. The phase relationship defining soil void ratio (e) is given by the ratio of the volume of
voids to the:
A. Total volume of soil mass
B. Volume of solid soil grains
C. Volume of water present in voids
D. Mass of dry solid particles
Rationale: Void ratio e is strictly defined as e = V_v / V_s, whereas porosity n is defined as V_v / V_t.
2. According to the Unified Soil Classification System (USCS), a fine-grained soil is
classified as a clay or silt based on its position relative to the 'A-line' on the Plasticity
Chart. The equation for the 'A-line' is:
A. PI = 0.73 * (LL - 20)
B. PI = 0.50 * (LL - 10)
C. PI = 0.90 * (LL - 30)
D. PI = 0.73 * (LL - 50)
Rationale: The USCS plasticity chart uses PI = 0.73(LL - 20) to separate inorganic clays (above the line)
from inorganic silts and organic soils (below the line).
3. Darcy's Law for one-dimensional fluid flow through porous soil media assumes that
flow velocity is directly proportional to the hydraulic gradient. This relationship holds
true strictly under:
, A. Turbulent flow conditions in coarse gravels
B. Laminar flow conditions in saturated soils
C. Unsaturated soils with variable air volume
D. High-velocity pipeline fluid dynamics
Rationale: Darcy's law v = k*i applies only when flow through pore channels is laminar (low Reynolds
numbers), typical of most saturated sands, silts, and clays.
4. Terzaghi's Principle of Effective Stress states that the effective vertical stress (σ')
acting on a soil skeleton equals total stress (σ) minus:
A. Hydraulic gradient pressure
B. Pore water pressure (u)
C. Overburden bulk density
D. Lateral earth pressure coefficient
Rationale: Effective stress controls soil strength and volume change, defined by Terzaghi's equation σ' =
σ - u.
5. Quick Condition (or quicksand condition) in cohesionless granular soils occurs when
the upward hydraulic gradient reaches the critical hydraulic gradient (i_cr), which
causes:
A. Effective stress to drop to zero, completely destroying shear strength
B. Total stress to double in magnitude
C. Permeability to fall to zero
D. Soil dry density to reach maximum index value
Rationale: When upward seepage drag balances submerged unit weight, u = σ, causing σ' = 0 and
reducing shear strength in cohesionless soils (τ = σ' tan φ) to zero.
6. In Terzaghi's 1-D Consolidation theory, the Time Factor (T_v) is mathematically
expressed as:
A. T_v = (c_v * H_d^2) / t
B. T_v = (c_v * t) / H_d^2
C. T_v = (k * t) / (m_v * γ_w)
D. T_v = (t * H_d) / c_v
Rationale: The dimensionless time factor T_v relates consolidation coefficient c_v, elapsed time t, and
, drainage path length H_d via T_v = c_v * t / H_d^2.
7. A clay soil layer is subjected to double drainage conditions. If the total thickness of the
clay layer is 6 meters, the maximum length of the drainage path (H_d) is:
A. 6.0 meters
B. 3.0 meters
C. 1.5 meters
D. 12.0 meters
Rationale: With double drainage (top and bottom pervious boundaries), water escapes from both sides,
so H_d is half the total layer thickness: 6 m / 2 = 3 m.
8. Overconsolidation Ratio (OCR) of a soil deposit is defined as the ratio of:
A. Preconsolidation stress (σ'_p) to current effective vertical stress (σ'_v0)
B. Current effective stress to initial pore pressure
C. Total stress to effective stress
D. Unconfined compressive strength to remolded strength
Rationale: OCR = σ'_p / σ'_v0. An OCR > 1 indicates the soil experienced higher vertical effective
stresses in its geological history than at present.
9. The standard Mohr-Coulomb shear strength criterion defines shear strength (τ) of a
soil as a function of effective normal stress (σ') by:
A. τ = c' + σ' sin φ'
B. τ = c' + σ' tan φ'
C. τ = c' + σ' cos φ'
D. τ = σ' / tan φ'
Rationale: Mohr-Coulomb models shear resistance as a combination of effective cohesion intercept c' and
frictional resistance σ' tan φ'.
10. In a standard Consolidated-Undrained (CU) triaxial shear test on saturated clay, pore
water pressure is measured to determine:
A. The total friction angle only
