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GATE geotechnical engineering: 5 practice questions

By the PrepMatic team · Updated 9 Oct 2026 · 4 min read

Geotechnical Engineering is a section of its own in the GATE CE paper, and a good source of dependable marks. The questions are formula-based and rest on a few relationships: phase relations, effective stress, Mohr-Coulomb, Terzaghi's consolidation theory and the bearing capacity equation. The five original questions below take one from each.

What GATE tests in geotechnical engineering

Geotechnical Engineering is one of the eight sections of the GATE 2027 CE paper, and the topic list was revised, so confirm it on the official syllabus page. The standard content is classification and phase relations, permeability and seepage, effective stress, compaction, consolidation and settlement, shear strength, earth pressure, slope stability and foundations. The real paper also has MSQ and NAT questions; all five below are MCQ.

Practice questions

Question 1

A saturated clay has a water content of 25% and a specific gravity of solids of 2.70. Taking the unit weight of water as 9.81 kN/m³, the saturated unit weight of the clay is closest to:

• A. 17.2 kN/m³
• B. 18.6 kN/m³
• C. 19.8 kN/m³
• D. 21.3 kN/m³

Question 2

A soil profile has 3 m of sand above the water table, with a unit weight of 16 kN/m³, over a thick saturated clay layer with a saturated unit weight of 19 kN/m³. The water table is at the sand-clay interface. Taking γw = 10 kN/m³, the effective vertical stress at a depth of 5 m is:

• A. 56 kPa
• B. 66 kPa
• C. 76 kPa
• D. 86 kPa

Question 3

A dry sand (effective cohesion 0, effective friction angle 30 degrees) is tested in a triaxial cell with an effective confining pressure of 100 kPa. At failure, the major effective principal stress is:

• A. 300 kPa
• B. 200 kPa
• C. 173 kPa
• D. 100 kPa

Question 4

A clay layer drained only at its top takes 8 years to reach 50% consolidation. If the same layer were drained at both top and bottom, the time to reach 50% consolidation would be:

• A. 0.5 years
• B. 1 year
• C. 1.5 years
• D. 2 years

Question 5

A strip footing rests on saturated clay with cu = 50 kPa and φ = 0, at a depth Df = 1 m below the surface. The soil unit weight is 18 kN/m³. Take Nc = 5.7, Nq = 1 and Nγ = 0. With a factor of safety of 3 on the net ultimate bearing capacity, the net safe bearing capacity is:

• A. 95 kPa
• B. 101 kPa
• C. 113 kPa
• D. 303 kPa

Answers and explanations

1. C. For a saturated soil, the void ratio is e = w Gs = 0.25 × 2.70 = 0.675. The saturated unit weight is γsat = (Gs + e) γw / (1 + e) = (2.70 + 0.675) × 9.81 / 1.675 = 3.375 × 9.81 / 1.675 = 19.8 kN/m³.
2. B. The total stress at 5 m is 3 × 16 + 2 × 19 = 48 + 38 = 86 kPa. The pore water pressure is zero in the sand above the water table and 2 m × 10 = 20 kPa at 5 m depth. The effective stress is σ′ = σ − u = 86 − 20 = 66 kPa.
3. A. For a cohesionless soil at failure, σ1′ = σ3′ tan²(45° + φ′/2) = 100 × tan² 60° = 100 × 3 = 300 kPa. Option C comes from forgetting the square. Option B uses 1 / (1 − sin φ′) instead of (1 + sin φ′) / (1 − sin φ′).
4. D. In Terzaghi's theory the time for a given degree of consolidation is proportional to the square of the longest drainage path. Single drainage has a path equal to the layer thickness H, and double drainage has H/2. So the time falls to 1/4: 8 / 4 = 2 years.
5. A. The net ultimate bearing capacity is qnu = c Nc + γ Df (Nq − 1) = 50 × 5.7 + 0 = 285 kPa. The net safe bearing capacity is qnu / FS = 285 / 3 = 95 kPa. Option B divides the gross capacity (303) by 3, option C adds the overburden back (the safe, not the net safe, value) and option D is the gross ultimate capacity.

How to prepare geotechnical engineering

• Draw the three-phase diagram for every phase-relation problem. Take Vs = 1 or V = 1, fill the blocks, and read off e, n, S, w and the unit weights.
• Compute effective stress layer by layer. Write a column of depth, total stress, pore pressure and effective stress, and watch the water table and capillary rise.
• Know the Mohr-Coulomb relations for σ1 and σ3 at failure, the UU, CU and CD triaxial tests, and the failure-plane angle of 45° + φ/2.
• Learn Terzaghi's consolidation theory: the time factor T = cv t / Hdr², the single versus double drainage rule, and the settlement formulas for normally and over-consolidated clays.
• Memorise the bearing capacity expressions and the definitions of gross, net and safe capacity, which are easy to confuse, as the options in Question 5 show. Add Rankine earth pressure with surcharge and water table effects.

Geotechnical engineering connects to fluid mechanics through seepage and to strength of materials through stress concepts. Structural analysis is the other major CE subject, and the GATE civil preparation guide lays out all eight sections.

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