NCEES Geotechnical Engineering 1 — Questions and Answers
Question 1: On the NCEES PE Geotechnical exam, the effective stress in a saturated soil is calculated as:
- σ' = σ + u (total stress plus pore water pressure)
- σ' = σ − u (total stress minus pore water pressure) (Correct answer)
- σ' = u − σ (pore pressure minus total stress)
- σ' = γz (unit weight times depth only)
Correct answer: σ' = σ − u (total stress minus pore water pressure)
Effective stress σ' = σ − u: the stress carried by the soil skeleton equals total stress minus pore water pressure.
Question 2: In NCEES PE Geotechnical practice, the Standard Penetration Test (SPT) provides which index value?
- Undrained shear strength Su directly
- N-value: blow count per 12 inches of penetration (Correct answer)
- Cone resistance qc in MPa
- Pressuremeter modulus Em
Correct answer: N-value: blow count per 12 inches of penetration
The SPT measures N-value (blow count per foot), used to estimate relative density, friction angle, and bearing capacity.
Question 3: For the NCEES PE Geotechnical exam, Terzaghi's bearing capacity equation for a strip footing is:
- qu = cNc + qNq + 0.5γBNγ (Correct answer)
- qu = cNc × Fcs × Fqs × Fγs
- qu = Su × Nc (for undrained clay only)
- qu = N60 × B/30
Correct answer: qu = cNc + qNq + 0.5γBNγ
Terzaghi's bearing capacity for a strip footing: qu = cNc + qNq + 0.5γBNγ, using bearing capacity factors Nc, Nq, and Nγ.
Question 4: In NCEES PE Geotechnical engineering, the Unified Soil Classification System (USCS) classifies soils based primarily on:
- In-situ SPT N-values
- Grain size distribution and Atterberg limits (Correct answer)
- Organic content and color
- Field density and moisture content
Correct answer: Grain size distribution and Atterberg limits
USCS classifies soils using grain size analysis (gravel, sand, fines percentage) and Atterberg limits (LL, PL) for fine-grained soils.
Question 5: On the NCEES PE Geotechnical exam, the coefficient of consolidation Cv is used in:
- Calculating shear strength of granular soils
- Predicting the time rate of consolidation settlement (Correct answer)
- Estimating lateral earth pressure coefficients
- Computing pile skin friction capacity
Correct answer: Predicting the time rate of consolidation settlement
Cv governs the time rate of consolidation; higher Cv means faster drainage and faster settlement completion.
Question 6: In NCEES PE Geotechnical practice, the Rankine active earth pressure coefficient Ka for a cohesionless soil with friction angle φ is:
- Ka = tan²(45° + φ/2)
- Ka = tan²(45° − φ/2)
- Ka = (1 − sin φ)/(1 + sin φ)
- Both B and C are equivalent (Correct answer)
Correct answer: Both B and C are equivalent
Ka = tan²(45° − φ/2) = (1 − sin φ)/(1 + sin φ); both expressions are mathematically equivalent for Rankine active pressure.
NCEES Geotechnical Engineering 1
On the NCEES PE Geotechnical exam, the effective stress in a saturated soil is calculated as: