Geotechnical Engineering accounts for 10 to 15 questions on the FE Civil exam. Most of them start from the phase diagram, weight-volume relationships, void ratio, water content and unit weights, and build from there to effective stress, settlement, shear strength and bearing capacity. Making the phase relationships automatic pays off across the entire area.
The problems below come with full solutions that show every substitution, not just the result. Geotech is the area where a correct method combined with a mishandled unit weight produces a wrong answer that still looks reasonable, so read the solutions for where the total versus effective distinction enters, not only for the arithmetic.
Exam weight: NCEES lists Geotechnical Engineering at 10-15 questions of the 110-question FE Civil exam. Work each problem below on paper first, then reveal the worked solution — reading a solution you have not attempted builds recognition, not recall.
What NCEES Tests in Geotechnical Engineering
The NCEES outline covers index properties and soil classification, including USCS and AASHTO, Atterberg limits and gradation, along with phase relationships, effective and total stress, and pore pressure. Expect items that hand you two phase quantities and ask for a third, or that ask for the vertical effective stress at a given depth with a water table somewhere in the profile.
Beyond that it covers permeability and seepage, consolidation and settlement, shear strength through Mohr-Coulomb, slope stability, lateral earth pressure with Rankine and Coulomb coefficients, shallow and deep foundation bearing capacity, and earth retaining structures. Compaction, subsurface exploration and standard penetration testing appear as well, usually as interpretation rather than computation, such as estimating relative density or strength from N-values.
5 Free Geotechnical Engineering Practice Problems
Each geotechnical engineering problem below comes from the FEExamClick FE Civil question bank, with worked solutions, and matches the style, difficulty and format of the real exam. Attempt each one under a three-minute limit — roughly the pace the exam demands.
Problem 1 — E. Stability of retaining structures (e.g., active/passive/at-rest pressure)
A rigid wall (at-rest) retains \( H = 6.0\,\mathrm{m} \) of sand with \( \phi = 30^\circ \) and \( \gamma = 18\,\mathrm{kN/m}^{3} \). Using Jaky \( K_0 \), what is the lateral pressure at the base \( \sigma_h(H) \) (\( \mathrm{kPa} \))?
Answer: C) \( 54\,\mathrm{kPa} \)
Step 1 – Identify given information: \( H = 6.0\,\text{m} \), \( \phi = 30^\circ \), \( \gamma = 18\,\text{kN/m}^3 \), rigid wall (at-rest condition).
Step 2 – At-rest lateral stress formula: \( K_0 = 1 - \sin\phi \) and \( \sigma_h = K_0 \gamma z \) at depth \( z = H \).
Step 3 – Solve:
$$K_0 = 1 - \sin 30^\circ = 1 - 0.5 = 0.5$$
$$\sigma_h = 0.5 \times 18 \times 6 = 54\,\text{kPa}$$
Step 4 – Answer: \( \sigma_h = 54\,\text{kPa} \) matches option (C). For comparison, the Rankine active pressure at the same depth would be \( K_a \gamma H = 0.333 \times 18 \times 6 = 36\,\text{kPa} \), which is 33% less.
Correct answer: (C)
Problem 2 — H. Foundation types (e.g., spread footings, deep foundations, wall footings, mats)
A strip footing must have no tension under service load \( P = 800\,\mathrm{kN} \) and service moment \( M = 500\,\mathrm{kN{\cdot}m} \) (per meter length). What minimum footing width \( B \) is required so the resultant stays within the middle third (\( e \leq B/6 \))?
Answer: B) \( 3.8\,\mathrm{m} \)
Step 1 – Identify given information: Service load \( P = 800\,\text{kN} \), service moment \( M = 500\,\text{kN{\cdot}m} \). Find minimum \( B \) for no tension (middle third rule).
Step 2 – Middle third (kern) criterion: No tension requires \( e \leq B/6 \), so \( B \geq 6e \) where \( e = M/P \).
Step 3 – Solve:
$$e = \dfrac{M}{P} = \dfrac{500}{800} = 0.625\,\text{m}$$
$$B \geq 6 \times 0.625 = 3.75 \approx 3.8\,\text{m}$$
Step 4 – Answer: \( B \geq 3.8\,\text{m} \) matches option (B). If \( B < 3.75\,\text{m} \), tension would develop at the heel, and the effective-width approach must be used instead of the linear distribution.
Option (D) uses the full footing width as the distance to the extreme fibre instead of half of it, doubling the flexural term and demanding a footing twice as wide as the kern rule actually requires. Options (A) and (C) do not follow from the data.
Correct answer: (B)
Problem 3 — I. Consolidation and differential settlement
A \( 12 \) ft thick clay layer is drained at both its top and its bottom boundaries and has a coefficient of consolidation \( c_v = 0.015 \) ft\(^2\)/day. Using the time factor table in the FE Handbook, how long after loading will the layer reach \( 90 \) per cent average consolidation?
Answer: C) \( 2{,}040\,\mathrm{days} \)
Step 1 – Identify given information: Layer thickness \( 12 \) ft, two-way drainage, \( c_v = 0.015 \) ft\(^2\)/day, \( U = 90\% \).
Step 2 – Drainage path and time factor (FE Handbook, p. 268): with drainage at both boundaries the water travels at most half the thickness, so \( H_{dr} = 12/2 = 6 \) ft. The table gives \( T_v = 0.848 \) at \( U = 90\% \), and \( T_v = c_vt/H_{dr}^2 \).
Step 3 – Solve:
\( t = \dfrac{T_vH_{dr}^2}{c_v} = \dfrac{0.848(6)^2}{0.015} = \dfrac{30.5}{0.015} = 2{,}035\,\text{days} \approx 2{,}040\,\text{days} \), about \( 5.6 \) years
Step 4 – Answer: \( t \approx 2{,}040 \) days matches option (C). Option (D) \( 8{,}140 \) days takes the drainage path as the full \( 12 \) ft, which is the one-way case; because \( H_{dr} \) is squared, that error costs a factor of four. Option (B) \( 473 \) days reads the table at \( U = 50\% \), \( T_v = 0.197 \), instead of \( 90\% \). Option (A) \( 339 \) days forgets to square \( H_{dr} \). The drainage condition is the single most consequential thing in a consolidation-time problem, and it is usually stated in one word of the stem.
Correct answer: (C)
Problem 4 — C. Laboratory and field tests
In a falling-head test, standpipe diameter = \( 6\,\mathrm{mm} \), specimen diameter = \( 50\,\mathrm{mm} \), specimen length \( L = 0.20\,\mathrm{m} \), time \( t = 180\,\mathrm{s} \), initial head \( h_1 = 0.80\,\mathrm{m} \), final head \( h_2 = 0.30\,\mathrm{m} \). What is \( k \) (\( \mathrm{m/s} \))?
Answer: B) \( 1.6 \times 10^{-5}\,\mathrm{m/s} \)
Step 1 – Identify the falling-head permeability formula:
From the FE Handbook:
$$ k = \frac{a \cdot L}{A \cdot t} \ln\left(\frac{h_1}{h_2}\right) $$
where:
- \( a \) = cross-sectional area of the standpipe
- \( A \) = cross-sectional area of the soil specimen
- \( L \) = length of the specimen
- \( t \) = elapsed time
- \( h_1, h_2 \) = initial and final heads in the standpipe
Step 2 – Compute the standpipe area \( a \):
$$ a = \frac{\pi d^2}{4} = \frac{\pi (0.006)^2}{4} = \frac{\pi \times 3.6 \times 10^{-5}}{4} = 2.827 \times 10^{-5} \,\mathrm{m}^{2} $$
Step 3 – Compute the specimen area \( A \):
$$ A = \frac{\pi D^2}{4} = \frac{\pi (0.05)^2}{4} = \frac{\pi \times 2.5 \times 10^{-3}}{4} = 1.963 \times 10^{-3} \,\mathrm{m}^{2} $$
Step 4 – Compute the natural log term:
$$ \ln\left(\frac{h_1}{h_2}\right) = \ln\left(\frac{0.80}{0.30}\right) = \ln(2.667) = 0.9808 $$
Step 5 – Substitute all values:
$$ k = \frac{(2.827 \times 10^{-5})(0.20)}{(1.963 \times 10^{-3})(180)} \times 0.9808 $$
$$ k = \frac{5.654 \times 10^{-6}}{0.3533} \times 0.9808 = 1.600 \times 10^{-5} \times 0.9808 $$
$$ k \approx 1.57 \times 10^{-5} \approx 1.6 \times 10^{-5} \,\mathrm{m/s} $$
Correct answer: (B)
Problem 5 — E. Stability of retaining structures (e.g., active/passive/at-rest pressure)
A braced excavation is designed using an apparent UNIFORM lateral pressure \( p = 600\,\mathrm{psf} \) over the full depth \( H = 20\,\mathrm{ft} \). Soldier piles are spaced \( s = 8\,\mathrm{ft} \) on center. What is the total lateral force tributary to ONE soldier pile (ignoring strut level effects), in kips?
Answer: D) \( 96\,\mathrm{kips} \)
Step 1 – Identify given information:
| Apparent lateral pressure | \( p = 600\,\text{psf} \) (uniform) |
| Excavation depth | \( H = 20\,\text{ft} \) |
| Soldier pile spacing | \( s = 8\,\text{ft} \) |
Step 2 – Tributary area method: Each soldier pile carries the lateral force acting on its tributary area \( H \times s \): \( F = p \times H \times s \)
Step 3 – Solve:
$$F = 600 \times 20 \times 8 = 96{,}000\,\text{lb} = 96\,\text{kips}$$
Step 4 – Answer: \( F = 96\,\text{kips} \) matches option (D). Option (A) is the force per foot of wall, \( pH = 12{,}000 \) lb, with the \( 8 \) ft tributary spacing never applied. Options (B) and (C) do not follow from the data. This total must be distributed among the strut levels supporting each soldier pile; the actual strut loads depend on their vertical spacing.
Correct answer: (D)
Using the FE Reference Handbook for Geotechnical Engineering
Keep the phase diagram and its identities in your head, because everything else in this section builds on them. In the handbook, searching Rankine reaches both the active and passive coefficients at once, and note that the bearing capacity factors Nc, Nq and N-gamma are tabulated against friction angle rather than something you compute under time pressure.
Four Mistakes That Cost Points
- Using total unit weight below the water table Effective stress below the water table uses the buoyant unit weight, saturated minus the unit weight of water. Applying total unit weight all the way down overstates effective stress and then cascades into wrong shear strength and bearing capacity. Sketch the profile, mark the water table, and label each layer before computing.
- Confusing void ratio with porosity Void ratio e is voids over solids; porosity n is voids over total volume, related by e equals n over one minus n. For typical soils the two values are close enough that a swap does not look obviously wrong. Rebuild the definition from the phase diagram instead of recalling a number.
- Applying Rankine when the geometry is not Rankine Rankine assumes a smooth vertical wall face and horizontal backfill. When the problem states wall friction or a sloped backfill, Coulomb applies and the coefficient differs. Read the described geometry before choosing the equation, because the distractors are typically built from the method you did not use.
- Dropping the surcharge term in bearing capacity The Nq term uses the overburden at the footing base, unit weight times embedment depth, not zero. Treating a footing as though it sits at ground surface discards a real share of the ultimate capacity. Confirm the embedment depth and whether the question wants ultimate or allowable capacity.
Frequently Asked Questions
How many geotechnical questions are on the FE Civil exam?
NCEES specifies 10 to 15 questions for Geotechnical Engineering out of the 110 on the exam. Because so much of the area chains off the phase diagram and effective stress, a few focused hours making those two topics automatic tends to lift performance across the whole block.
Is soil classification worth memorizing?
Memorize the logic, not the tables. The USCS and AASHTO charts are in the NCEES FE Reference Handbook, but you still need to know that you route first by percent passing the No. 200 sieve, then use Atterberg limits and the plasticity chart for the fines. Knowing the path makes the lookup fast.
Do geotechnical questions require Mohr circle work?
Sometimes, though usually in a light form: given principal stresses, find the shear stress on a plane, or given a failure envelope, find strength at a stated normal stress. You are rarely asked to construct a full circle graphically. Fluency with tau equals c plus sigma tangent phi covers most shear strength items.
What is the fastest way to improve in this area?
Drill phase relationship problems until conversions among void ratio, porosity, water content, specific gravity and unit weights take no thought, then move to effective stress profiles with a water table. Those two skills are prerequisites for consolidation, shear strength and bearing capacity, so gains there show up in questions that look unrelated.
Keep Going
Done with geotechnical engineering? Work through the other FE Civil knowledge areas with more free practice problems, review the full FE Civil exam topic breakdown, or plan your preparation with our FE exam study guide and study timeline. Or test yourself against the clock with the free FE Civil practice exam: 20 timed questions in the CBT format.