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Soil Mechanics MCQ Practice Set — 50 Questions with Answers

50 exam-oriented Soil Mechanics multiple-choice questions with the correct answer and a clear explanation for each. Frequently asked in AE Level Civil Engineering, JE Level Civil Engineering. Solve the full set below for free — no login required.

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  1. 1
    Soil MechanicsMEDIUM

    'Vibro-flotation' (vibro-compaction) is used to densify:

    AVery soft cohesive clays (undrained shear < 30 kPa)
    BLoose granular sand deposits — vibration liquefies temporarily, grains rearrange to denser state
    CRock masses
    DOrganic and peaty soils

    Answer: B. Loose granular sand deposits — vibration liquefies temporarily, grains rearrange to denser state

    Explanation: Vibro-compaction / vibroflotation: a vibrating probe (torpedo-shaped, 400 mm dia) penetrated into loose sand. Vibration (horizontal, 50 Hz) liquefies granular soil locally → sand grains rearrange under gravity to denser state. Sand backfill added from surface to fill voids. After withdrawal: stone column sometimes formed (vibro-replacement for cohesive soils). Suitable for: loose clean sand (< 15% fines).

  2. 2
    Soil MechanicsHARD

    The 'International Building Code' (IBC) and IS codes classify building sites for seismic design based on:

    ABuilding height and number of floors
    BShear wave velocity Vs,30 (or SPT N-value) in top 30 m — softer soil = higher amplification = more stringent seismic design
    CRainfall intensity at the site
    DDistance from city centre

    Answer: B. Shear wave velocity Vs,30 (or SPT N-value) in top 30 m — softer soil = higher amplification = more stringent seismic design

    Explanation: Site classification for seismic design: based on average Vs,30 (shear wave velocity in top 30 m) or SPT N-value: Rock (SA): Vs > 760 m/s; Hard soil (SB): 360–760; Medium (SC): 180–360; Soft (SD): < 180 m/s (IS 1893 Table 1 similar). Soft soils amplify ground motion (site amplification). SS (soft soil)/S1 (liquefiable) sites require special analysis. IS 1893 uses soil type I, II, III (similar principle).

  3. 3
    Soil MechanicsHARD

    The 'Hvorslev parameters' c_e and φ_e in soil mechanics refer to:

    ACompression index and swelling index
    BTrue intrinsic cohesion and friction at constant void ratio — separates structural effects from actual soil properties in OC clay
    CGrain size parameters d10 and d60
    DHydraulic conductivity in two directions

    Answer: B. True intrinsic cohesion and friction at constant void ratio — separates structural effects from actual soil properties in OC clay

    Explanation: Hvorslev (1937): true (intrinsic) cohesion c_e and true angle of friction φ_e of soil. From drained tests on OC clay: failure envelope in (e, σ') space rather than simple Mohr-Coulomb in (τ, σ') space. The apparent c in Mohr-Coulomb is due to overconsolidation (structure/cementation). At same void ratio: τf = c_e + σ'×tanφ_e (Hvorslev). Shows that φ_e is nearly constant; OCR controls apparent cohesion.

  4. 4
    Soil MechanicsEASY

    The 'IS 2911' code series covers:

    AOnly retaining wall design
    BDesign and construction of pile foundations — covers bored, precast, driven, timber, and under-reamed piles
    CShallow foundation bearing capacity only
    DSoil exploration methods

    Answer: B. Design and construction of pile foundations — covers bored, precast, driven, timber, and under-reamed piles

    Explanation: IS 2911: Design and Construction of Pile Foundations. Parts: (1) Concrete piles (bored cast-in-situ, precast, driven); (2) Timber piles; (3) Under-reamed piles; (4) Load tests on piles. IS 2911 Part 4: Static load test on piles (maintained load test). Companion: IS 14593 (bore pile quality). IS 2950 (open foundation), IS 1080 (shallow foundation). IS 2911 is the primary pile code used by practising engineers.

  5. 5
    Soil MechanicsMEDIUM

    The 'cement stabilisation' of sub-base material for roads (IS 4332 Part 4) improves:

    AReducing bearing capacity of soil
    BIncreases UCS, reduces plasticity and swell, improves stiffness — through C-S-H cementation of soil particles
    CMaking soil more plastic and compressible
    DOnly useful for clay soils above 50% fines

    Answer: B. Increases UCS, reduces plasticity and swell, improves stiffness — through C-S-H cementation of soil particles

    Explanation: Cement stabilisation: 3–8% cement mixed with soil. Benefits: (1) Increases UCS (IS 4332: 7-day soaked UCS 1.7–3.5 MPa for sub-base); (2) Reduces plasticity; (3) Reduces swell; (4) Increases stiffness (CBR). C-S-H gel forms between cement and soil particles. Best for: sands, sandy clays, silts. Poorly suited for: organic soils, high sulphate soils (ettringite forms). IRC:50 covers cement-treated sub-base (CTB).

  6. 6
    Soil MechanicsMEDIUM

    The 'shear strength' of soil measured in an 'undrained triaxial test' (UU test) is:

    ADependent on effective confining pressure
    BConstant Su = (σ1-σ3)/2 regardless of cell pressure for saturated clay (φu=0 — effective stress unchanged during shearing)
    COnly for dry sands
    DSum of c and tanφ times confining pressure

    Answer: B. Constant Su = (σ1-σ3)/2 regardless of cell pressure for saturated clay (φu=0 — effective stress unchanged during shearing)

    Explanation: UU triaxial test: no drainage permitted during cell pressure application or shear. For saturated clay: increase in cell pressure = increase in pore pressure → effective stress unchanged → failure envelope is horizontal (φu = 0). Su = (σ1-σ3)/2 = constant regardless of cell pressure. Results: total stress envelope only. Used for: rapid loading problems (embankment stability at end of construction in soft clay).

  7. 7
    Soil MechanicsMEDIUM

    The 'primary consolidation' of a clay layer settles because:

    AImmediate elastic compression of soil grains
    BDissipation of excess pore water pressure → effective stress increase → void ratio decrease (water squeezed out)
    CErosion of clay particles
    DSwelling of clay minerals on wetting

    Answer: B. Dissipation of excess pore water pressure → effective stress increase → void ratio decrease (water squeezed out)

    Explanation: Primary consolidation: excess pore water pressure (generated by load application) dissipates through drainage → effective stress increases → volume decreases. Time rate: cv×t/H²_dr (Tv = dimensionless time factor). Final settlement: Δe/(1+e0)×H from oedometer Cc and pressure increment. Complete primary consolidation: u_excess → 0, effective stress = final applied stress. Secondary: continued creep after u=0.

  8. 8
    Soil MechanicsHARD

    The 'Swedish slip circle method' (Fellenius method) for slope stability is conservative because:

    AIt over-estimates shear resistance
    BNeglects inter-slice forces → under-estimates normal stress on slip surface → under-estimates friction resistance → lower FOS
    CIt always gives FOS > 2.0
    DIt assumes no friction (φ=0 always)

    Answer: B. Neglects inter-slice forces → under-estimates normal stress on slip surface → under-estimates friction resistance → lower FOS

    Explanation: Fellenius/Ordinary Method of Slices: assumes inter-slice forces are parallel to slice base (zero inter-slice shear and normal). This under-estimates normal force on slip surface → under-estimates shear resistance → FOS lower than actual. Typically FOS(OMS) = 5–20% lower than Bishop's. Very conservative for φ > 0 soils. Still used for preliminary checks. More accurate: Bishop''s simplified or Spencer''s method.

  9. 9
    Soil MechanicsMEDIUM

    The 'creep' behaviour of soil under long-term sustained load is called:

    AImmediate elastic compression on loading
    BSecondary consolidation — volume change under constant effective stress due to viscous particle rearrangement (creep)
    CSwelling on unloading
    DPiping failure of sand

    Answer: B. Secondary consolidation — volume change under constant effective stress due to viscous particle rearrangement (creep)

    Explanation: Secondary consolidation (creep): volume change (compression) occurring at constant effective stress, after primary consolidation (excess pore pressure fully dissipated). Due to: plastic rearrangement of soil fabric (clay particles, organic matter). Cα = secondary compression index = Δe/Δlog(t). Significant in: highly organic soils, soft clays, peat. Cα/(Cc) ≈ 0.04–0.06 for inorganic clays, 0.05–0.1 for organics.

  10. 10
    Soil MechanicsHARD

    'Compaction grouting' as a ground improvement technique involves:

    AInjecting liquid to permeate soil pores
    BInjecting very stiff grout bulbs that densify loose surrounding soil by lateral displacement
    CMixing cement into soil with auger
    DFreezing the soil

    Answer: B. Injecting very stiff grout bulbs that densify loose surrounding soil by lateral displacement

    Explanation: Compaction grouting: very low-slump (0–25 mm) cement-sand grout injected under high pressure into loose soil through small-diameter pipes. Grout forms a bulb; does NOT penetrate soil pores (like permeation grouting). Instead, the expanding bulb densifies surrounding soil by displacement. Used for: loose sand, collapsible soils, utility corridor remediation. Controlled by monitoring injection pressure and volume.

  11. 11
    Soil MechanicsMEDIUM

    The 'grouting' method used to fill large voids in karstic limestone is:

    ACompaction grouting (too viscous for large voids)
    BBulk (filling) grouting — cement-bentonite slurry poured or pumped into large karstic voids and mine workings
    CChemical grouting with silicates only
    DElectro-osmosis (for cohesive soils only)

    Answer: B. Bulk (filling) grouting — cement-bentonite slurry poured or pumped into large karstic voids and mine workings

    Explanation: Types of grouting: (1) Permeation (chemical) grouting: low-viscosity chemicals (sodium silicate, acrylate) for fine sands; (2) Compaction grouting: stiff grout densifies loose soil; (3) Jet grouting: high-pressure jet cuts soil + grout forms column; (4) Bulk/filling grouting: cement-bentonite slurry poured into large voids (karst caves, old mine workings, tunnels). Karst voids: drilling + gravity/low-pressure cement filling.

  12. 12
    Soil MechanicsHARD

    The 'consolidation settlement' of a clay layer can be separated into:

    AOnly one type of settlement exists
    BImmediate (elastic), primary consolidation (pore pressure dissipation), and secondary (creep) settlements
    COnly immediate and secondary
    DConsolidation and shear failure settlements

    Answer: B. Immediate (elastic), primary consolidation (pore pressure dissipation), and secondary (creep) settlements

    Explanation: Total consolidation settlement = Immediate (elastic) settlement (Si) + Primary consolidation settlement (Sc) + Secondary consolidation settlement (Ss). Si: elastic compression of clay (undrained, instant). Sc: time-dependent primary (pore pressure dissipation). Ss: creep of soil skeleton (constant effective stress, beyond 100% consolidation). For soft clays: Sc >> Si >> Ss. For overconsolidated stiff clays: Si dominates.

  13. 13
    Soil MechanicsHARD

    The 'bishop''s simplified method' for circular slip surface analysis computes FOS by:

    AInfinite slope analysis (no slices)
    BVertical slice method with moment equilibrium and iteration: FOS=Σ(resistance)/Σ(driving) accounting for pore pressure u
    CRankine earth pressure at the toe
    DOnly the most critical slip surface without iteration

    Answer: B. Vertical slice method with moment equilibrium and iteration: FOS=Σ(resistance)/Σ(driving) accounting for pore pressure u

    Explanation: Bishop''s simplified: slip circle; divides into vertical slices. FOS = Σ[c'b + (W-ub)tanφ'] / mα / ΣW sinα where mα = cosα + sinα×tanφ'/FOS (requires iteration). Simplified: ignores inter-slice shear forces (retains inter-slice normal). More accurate than Ordinary Method of Slices (OMS/Fellenius). For most soil conditions: Bishop's gives FOS ≈ 0–15% higher than OMS. Standard for circular failure in homogeneous slopes.

  14. 14
    Soil MechanicsMEDIUM

    The 'strut and waler' support system in a braced excavation works as:

    AThe struts carry tension like cables
    BHorizontal compression members (struts) supported by walers distribute active earth pressure across the excavation
    COnly for water control (no structural role)
    DStruts are always pre-cast concrete panels

    Answer: B. Horizontal compression members (struts) supported by walers distribute active earth pressure across the excavation

    Explanation: Braced excavation: as excavation proceeds, horizontal steel struts (or tie-backs) installed at intervals to support sheeting/piling. Walers: horizontal beams distributing load from sheeting to struts. Struts: horizontal compression members transmitting force across excavation. Hydraulic struts: allow pre-loading to reduce wall deflection. Failure modes: strut buckling (slender struts), waler failure, strut connection failure.

  15. 15
    Soil MechanicsHARD

    'Rock mass classification' by 'RMR' (Rock Mass Rating, Bieniawski) considers:

    AOnly uniaxial compressive strength
    BUCS + RQD + joint spacing + joint condition + groundwater + orientation adjustment — 6 parameters total, 0–100 score
    COnly the depth of the rock mass
    DChemical composition of rock

    Answer: B. UCS + RQD + joint spacing + joint condition + groundwater + orientation adjustment — 6 parameters total, 0–100 score

    Explanation: Bieniawski RMR (1973): 6 parameters: (1) UCS of intact rock (0–15 pts); (2) RQD (3–20 pts); (3) Spacing of discontinuities (5–20 pts); (4) Condition of discontinuities (0–30 pts); (5) Groundwater condition (0–15 pts); (6) Orientation of discontinuities (adjustment −12 to 0 pts). Total RMR 0–100. Class I (81–100): very good; II (61–80): good; III (41–60): fair; IV (21–40): poor; V (0–20): very poor rock. Used for: tunnel support design.

  16. 16
    Soil MechanicsMEDIUM

    The 'differential settlement' between two footings is more harmful than total settlement because:

    ATotal settlement is easy to measure accurately
    BDifferential settlement causes angular distortion → structural cracking and tilting; uniform total settlement less harmful
    CTotal settlement always causes collapse
    DDifferential settlement only affects wooden structures

    Answer: B. Differential settlement causes angular distortion → structural cracking and tilting; uniform total settlement less harmful

    Explanation: Differential settlement: unequal settlement of foundations → angular distortion (δ/L). Structural damage thresholds: angular distortion 1/500 for sensitive structures; 1/300 for RC frames with brick infill; 1/150 for steel frames with brick panels. Even if total settlement is large but uniform (no differential), structure may still function. Differential settlement causes: tilt, cracking, structural distress, sinking at one end.

  17. 17
    Soil MechanicsHARD

    In the 'Cam Clay model' for soil behaviour, the 'yield surface' represents:

    AThe boundary below which no stress can exist
    BBoundary separating elastic (inside) from elastoplastic (outside) behaviour in p'−q space for clay
    CThe shear strength failure line only
    DCreep behaviour of clay

    Answer: B. Boundary separating elastic (inside) from elastoplastic (outside) behaviour in p'−q space for clay

    Explanation: Cam Clay: critical state model for normally consolidated clays. Yield surface (ellipse in p'-q space where p' = mean effective stress, q = deviatoric stress) separates: (1) Inside — elastic (recoverable) behaviour; (2) Outside — elastoplastic (volumetric yielding, compression). The surface passes through origin and critical state line intersection. Hardening: yield surface expands with plastic compression. Widely used in FEM for clay.

  18. 18
    Soil MechanicsMEDIUM

    'Peat' soils in geotechnical engineering are problematic because:

    APeat has very high strength (low water content)
    BVery high compressibility, low strength, high long-term secondary compression — large prolonged settlements make foundation design very difficult
    CPeat is too hard to excavate
    DPeat swells excessively on wetting

    Answer: B. Very high compressibility, low strength, high long-term secondary compression — large prolonged settlements make foundation design very difficult

    Explanation: Peat: highly organic (> 75% organic content), very high void ratio (e = 5–15), high compressibility (Cc = 1–3), very low shear strength (Su = 5–20 kPa), very high secondary compression (Cα/Cc = 0.05–0.07). Settlement: large, slow, ongoing for decades. Not suitable for direct foundation without treatment. Treatment: (1) Remove and replace; (2) Deep mixing with lime/cement; (3) Pre-loading with wick drains; (4) Avoid (bridge over peat).

  19. 19
    Soil MechanicsHARD

    The 'residual shear strength' of over-consolidated clay is relevant for:

    AFresh compacted fill with no slip history
    BExisting (reactivated) slip surfaces in OC clay — platelet alignment gives lowest possible φ'r; must use residual for old landslides
    CSand liquefaction analysis
    DPile design in soft clay

    Answer: B. Existing (reactivated) slip surfaces in OC clay — platelet alignment gives lowest possible φ'r; must use residual for old landslides

    Explanation: Residual strength: after large displacement (existing slip surface) φ'_r = much lower than peak φ'p; c'_r ≈ 0. Clay platelets align parallel to slip plane → very low friction. φ'_r = 8–15° for high-plasticity clays (bentonite); 20–25° for low-plasticity. Used in: stability analysis of first-time and reactivated landslides, old dam failures (sliding along pre-existing slip surface). Must be used if reactivation of old slip is possible.

  20. 20
    Soil MechanicsHARD

    The 'quick clay' behaviour observed in sensitive Scandinavian clays is due to:

    AVery high organic content making clay buoyant
    BLeached marine clay — loss of salt destroys flocculated structure; disturbance collapses cemented fabric to near-fluid slurry
    CPresence of coarse sand layers
    DHigh temperature melting clay minerals

    Answer: B. Leached marine clay — loss of salt destroys flocculated structure; disturbance collapses cemented fabric to near-fluid slurry

    Explanation: Quick clay: marine clay deposited in saline water (Na⁺ in pores keeps clay flocculated). Later leached by freshwater → Na⁺ replaced by water → highly unstable structure maintained only by cementation and structure. On disturbance (liquefaction): structure collapses, strength drops to near-zero → liquid. St > 100. Cannot be predicted by simple tests. Causes massive landslides (e.g., Rissa 1978 Norway). Indian analogy: very soft marine clays.

  21. 21
    Soil MechanicsHARD

    A 'diaphragm wall' (slurry wall) for deep basement excavation is constructed by:

    ADriving steel sheet piles with vibratory hammer
    BTrenching under bentonite slurry, placing rebar cage, tremie concrete from bottom — forms permanent RC panel
    CInjecting concrete grout only
    DInstalling pre-cast panels from surface

    Answer: B. Trenching under bentonite slurry, placing rebar cage, tremie concrete from bottom — forms permanent RC panel

    Explanation: Diaphragm wall: trench excavated panel by panel (3–6 m long) under bentonite slurry (supports trench stability by hydrostatic pressure). Rebar cage lowered. Concrete tremied from bottom displacing slurry. Panels joined by stop-end pipes or water-stops. Walls reach 30–60 m depth. Functions: (1) Permanent basement wall; (2) Water cutoff; (3) Retaining wall during excavation. Used in: Mumbai metro, Kolkata metro stations, high-rise basements.

  22. 22
    Soil MechanicsHARD

    The 'pressuremeter test' (PMT) in a borehole measures:

    AVertical stress at depth only
    BIn-situ horizontal stress and soil stiffness from inflating probe against borehole wall — limit pressure and pressuremeter modulus
    COnly soil moisture content
    DShear strength by driving a cone

    Answer: B. In-situ horizontal stress and soil stiffness from inflating probe against borehole wall — limit pressure and pressuremeter modulus

    Explanation: Pressuremeter: cylindrical probe inflated in borehole under controlled pressure. Measures volume of water pumped in vs pressure applied → pressure-volume curve. From curve: (1) Limit pressure pL (equivalent to passive resistance); (2) Ménard pressuremeter modulus EM (soil stiffness); (3) KH0 (at-rest horizontal stress from lift-off pressure). Used for: foundation design in French practice (Ménard), pile design (semi-empirical), creep coefficient for settlements.

  23. 23
    Soil MechanicsHARD

    The 'arching effect' in soils explains why:

    AMore load is applied to yielding part
    BLoad transfers from yielding to stationary soil through shear → less load on structure than full overburden weight
    CArching only occurs in dry sand
    DArching is only relevant in rock tunnels

    Answer: B. Load transfers from yielding to stationary soil through shear → less load on structure than full overburden weight

    Explanation: Arching (Terzaghi, 1943): when one portion of soil mass yields relative to adjacent stationary mass → shear stresses develop along failure surface → load transferred from yielding to stationary soil. Examples: (1) Load on buried pipe less than full weight of overburden (negative arching when pipe settles); (2) Tunnel lining carries much less than full overburden; (3) Silo bin pressures (Janssen) less than full column weight. Arching = soil''s self-supporting ability.

  24. 24
    Soil MechanicsHARD

    The 'geosynthetic reinforced soil wall' (GRS) functions by:

    ALike a concrete gravity retaining wall (no reinforcement needed)
    BHorizontal geosynthetic layers in compacted fill carry tension, confining soil and enabling stable steep-faced walls
    CThe facing alone carries all loads
    DBy pre-stressing the soil

    Answer: B. Horizontal geosynthetic layers in compacted fill carry tension, confining soil and enabling stable steep-faced walls

    Explanation: GRS (Geosynthetic Reinforced Soil) retaining wall: geogrid or geotextile layers placed horizontally in compacted soil fill. Reinforcement acts as tensile member; mobilises friction from surrounding soil. Equivalent to increasing horizontal confining stress. Construction: wrapped face or block/panel face. Analysis: internal stability (tensile failure of geogrid, pullout) and external stability (overturning, sliding, bearing). Cost 30–50% less than concrete retaining walls.

  25. 25
    Soil MechanicsHARD

    The 'observational method' in geotechnical engineering (Peck, 1969) involves:

    AUsing maximum possible loads for design (no flexibility)
    BDesign-as-you-go: construct incrementally monitoring actual behaviour; pre-planned contingencies if limits exceeded
    CUsing only laboratory test results without field verification
    DRandom design without any monitoring

    Answer: B. Design-as-you-go: construct incrementally monitoring actual behaviour; pre-planned contingencies if limits exceeded

    Explanation: Observational method: (1) Design on best estimate of properties; (2) Define acceptable limits; (3) Select monitoring scheme; (4) Plan contingency measures; (5) Monitor during construction; (6) Modify design if needed. Particularly suitable when: soil variability high, properties uncertain, failure mode well-defined. Examples: embankment on soft clay with pore pressure monitoring, piled foundation monitoring. Avoids: over-conservative design AND unexpected failure.

  26. 26
    Soil MechanicsHARD

    'Ground anchors' (soil nails or rock anchors) in deep excavations resist:

    AOnly compression loads on wall
    BTensile forces from wall/slope wanting to move — anchor transfers tension to stable ground through grouted fixed zone
    CSeismic vibration only
    DWind loads on adjacent buildings

    Answer: B. Tensile forces from wall/slope wanting to move — anchor transfers tension to stable ground through grouted fixed zone

    Explanation: Ground anchor: steel tendon or bar drilled into soil/rock at angle; grouted in at fixed length; pre-stressed against anchor head on wall. Transfers tensile force to stable ground beyond failure wedge. Used for: (1) Retaining wall tie-back (prevents overturning/sliding); (2) Foundation uplift resistance; (3) Slope stabilisation. Pre-stressed anchors: minimise wall deflection. IS 14448 covers soil anchors. Load test: proof load test (110% design load).

  27. 27
    Permeability Falling HeadMEDIUM

    In a falling head permeability test, the coefficient of permeability k is given by:

    Ak = aL/(At) × ln(h₁/h₂)
    Bk = Q×L/(A×h×t)
    Ck = iA/Q
    Dk = v/i

    Answer: A. k = aL/(At) × ln(h₁/h₂)

    Explanation: Falling head test: k = (a×L)/(A×t) × ln(h₁/h₂) = (a×L)/(A×t) × 2.303×log(h₁/h₂), where a = area of standpipe, A = area of sample, L = length of sample, h₁ = initial head, h₂ = final head, t = time elapsed.

  28. 28
    Soil MechanicsMEDIUM

    The shrinkage index in a soil test is equal to

    APlastic Limit - Shrinkage Limit
    BLiquid Limit - Plastic Limit
    CLiquid Limit - Shrinkage Limit
    DPlastic Limit - Liquid Limit

    Answer: A. Plastic Limit - Shrinkage Limit

    Explanation: Shrinkage Index is defined as the difference between the plastic limit and the shrinkage limit (Ip = PL - SL).

  29. 29
    Soil MechanicsMEDIUM

    The tendency for general shear failure of an isolated footing in sand, in general, decreases with

    Adecreasing footing depth
    Bincreasing footing width
    Cdecreasing soil-grain compressibility
    Dincreasing relative density of the sand

    Answer: A. decreasing footing depth

    Explanation: General shear failure is associated with dense sands and shallow depths. As the depth of the footing increases, the failure mode tends to shift from general shear to local or punching shear. Therefore, decreasing the depth increases the likelihood of general shear failure, while increasing the depth decreases it.

  30. 30
    Compaction TestMEDIUM

    In Standard Proctor compaction test, the compaction energy per unit volume used is:

    A593 kJ/m³
    B604 kJ/m³
    C2674 kJ/m³
    D1200 kJ/m³

    Answer: A. 593 kJ/m³

    Explanation: Standard Proctor compaction energy is approximately 593 kJ/m³. The calculation is (3 layers * 25 blows * 2.5 kg * 9.81 m/s² * 0.305 m) / 0.000944 m³ = 593 kJ/m³.

  31. 31
    Soil MechanicsMEDIUM

    In the slope-deflection method, the deformation is primarily considered to be caused by

    Abending moment
    Bshear force
    Caxial force
    Dtorsion

    Answer: A. bending moment

    Explanation: The slope-deflection method is based on the Euler-Bernoulli beam theory, which assumes that deformations due to bending moments are significant, while deformations due to shear and axial forces are neglected.

  32. 32
    Index PropertiesMEDIUM

    The flow curve in a liquid limit test (Casagrande device) plots water content vs number of blows on semi-log scale. The slope of this line is:

    APlasticity index
    BFlow index
    CConsistency index
    DToughness index

    Answer: B. Flow index

    Explanation: Flow index If = slope of flow curve = (w1−w2)/log(N2/N1). It represents rate of loss of shear strength with water content.

  33. 33
    Seepage AnalysisHARD

    The Laplace equation governing 2D steady seepage is:

    A∂u/∂t = Cv(∂²u/∂z²)
    B∂²h/∂x² + ∂²h/∂z² = 0
    C∂h/∂t = k∇²h
    Dq = kiA

    Answer: B. ∂²h/∂x² + ∂²h/∂z² = 0

    Explanation: Laplace equation for 2D seepage (isotropic soil): ∂²h/∂x² + ∂²h/∂z² = 0. For anisotropic: kx∂²h/∂x² + kz∂²h/∂z² = 0, which transforms to Laplace by coordinate scaling.

  34. 34
    Earth PressureMEDIUM

    For a dry cohesionless soil with unit weight 18 kN/m³, φ=30°, and wall height 5m, the total active earth pressure (Rankine) per metre length is:

    A75 kN/m
    B135 kN/m
    C45 kN/m
    D90 kN/m

    Answer: A. 75 kN/m

    Explanation: Ka=tan²(45−φ/2)=tan²(30°)=(0.577)²=0.333. Pa=½×Ka×γ×H²=½×0.333×18×25=75 kN/m. Acts at H/3=1.67m from base.

  35. 35
    Soil MechanicsMEDIUM

    The 'bearing capacity' of soil increases with depth because:

    AGroundwater table always rises with depth
    BOverburden surcharge q=γDf increases with depth, increasing contribution of Nq term in Terzaghi''s BC formula
    CTemperature is higher at depth
    DBC is constant with depth

    Answer: B. Overburden surcharge q=γDf increases with depth, increasing contribution of Nq term in Terzaghi''s BC formula

    Explanation: BC increases with depth: (1) Terzaghi formula: qu = cNc + qNq + 0.5γBNγ where q = γDf (surcharge from overburden) increases with depth Df; (2) For cohesionless soils (c=0): qu = qNq + 0.5γBNγ — both q and γ terms increase; (3) Confinement from overburden increases friction mobilisation. This is why deep foundations (piles) can carry much higher loads than shallow footings.

  36. 36
    Soil MechanicsHARD

    The 'dilatancy correction' in SPT for fine sands below water table is applied when N exceeds:

    AN > 30 for all soil types
    BN > 15 for fine sands/silts below water table — actual N overestimates true density due to negative pore pressure during driving
    CN < 5 for soft clays
    DN > 60 (never needed in practice)

    Answer: B. N > 15 for fine sands/silts below water table — actual N overestimates true density due to negative pore pressure during driving

    Explanation: IS 2131 / Terzaghi correction: in saturated fine sands and silts: high SPT N (>15) → pore water suction develops during driving → apparent stiffness increase. Dilatancy correction: N_corrected = 15 + 0.5(N_actual − 15) when N > 15. But only for fine sands below WT (not coarse sands). Reduces N to account for pore pressure effect. Applied BEFORE overburden correction in some methods.

  37. 37
    Soil MechanicsHARD

    The 'group efficiency' of pile groups is generally less than 1.0 in:

    ADense sand deposits where piles densify surrounding soil
    BClay soils — overlapping stress/strain zones reduce group capacity per pile below individual pile capacity
    COnly for single piles not grouped
    DAll soils equally

    Answer: B. Clay soils — overlapping stress/strain zones reduce group capacity per pile below individual pile capacity

    Explanation: Pile group efficiency η = Q_group / (n × Q_single). In clays (cohesive soils): group efficiency < 1 due to overlapping stress zones → group settles more and has lower capacity per pile. In sands (cohesionless): group efficiency can be > 1 (densification effect). Converse-Labarre formula: η = 1 − φ[(n_cols−1)n_rows + (n_rows−1)n_cols] / (90 × n_cols × n_rows). Block failure also checked.

  38. 38
    Soil Mechanics and Foundation EngineeringHARD

    For dry sand with gamma = 18 kN/m3, H = 4 m and Ka = 1/3, active thrust per metre length is:

    A96 kN/m
    B72 kN/m
    C24 kN/m
    D48 kN/m

    Answer: D. 48 kN/m

    Explanation: Pa = 0.5 Ka gamma H^2 = 0.5 x 1/3 x 18 x 16 = 48 kN/m.

  39. 39
    Terzaghi Consolidation TheoryMEDIUM

    According to Terzaghi one-dimensional consolidation theory, the degree of consolidation U at time factor Tv = 0.197 is approximately:

    A10%
    B50%
    C90%
    D25%

    Answer: B. 50%

    Explanation: Terzaghi consolidation: Tv = pi/4 * (U%)^2 / 10000 for U < 60%. At U=50%: Tv = pi/4 * (50)^2 / 10000 = 0.196 approximately 0.197. At U=90%: Tv = 0.848. The time factor Tv = Cv*t/Hd^2 (Cv = coefficient of consolidation, Hd = drainage path = H/2 for doubly drained layer).

  40. 40
    Soil Mechanics and Foundation EngineeringMEDIUM

    The undrained shear strength of clay from unconfined compression test is:

    ATwice the unconfined strength
    BZero always
    CHalf the unconfined compressive strength
    DEqual to unconfined strength

    Answer: C. Half the unconfined compressive strength

    Explanation: For saturated clay in unconfined compression, qu = 2cu.

  41. 41
    Pore Pressure ParametersMEDIUM

    Skempton pore pressure parameters A and B for a saturated soil under undrained loading relate excess pore pressure to principal stress increments as:

    ADelta u = B [Delta sigma_3 + A(Delta sigma_1)]
    BDelta u = B [Delta sigma_3 + A(Delta sigma_1 - Delta sigma_3)]
    CDelta u = A x Delta sigma_1 + B x Delta sigma_3
    DDelta u = (Delta sigma_1 + Delta sigma_3) / 2

    Answer: B. Delta u = B [Delta sigma_3 + A(Delta sigma_1 - Delta sigma_3)]

    Explanation: Skempton (1954): Delta_u = B[Delta_sigma_3 + A(Delta_sigma_1 - Delta_sigma_3)], where B = 1 for saturated soil (degree of saturation > 95%), A at failure: A = 0 to 0.5 for heavily OC clays; A = 0.5 to 1.0 for NC clays; A > 1.0 for very sensitive or loose sands. Negative A (OC clay) indicates tendency to dilate. Used in undrained triaxial analysis.

  42. 42
    Bearing Capacity Eccentric LoadMEDIUM

    Meyerhof's method for eccentric loading reduces the bearing capacity by using an effective footing dimension. For a footing of width B under eccentricity e, the effective width B' is:

    AB - e
    BB - 2e
    CB/2 + e
    D2(B/2 - e)

    Answer: B. B - 2e

    Explanation: Meyerhof's effective width concept: B' = B - 2e, L' = L - 2e_L (for two-way eccentricity). The effective area B'×L' is used to compute bearing pressure and bearing capacity, ensuring uniform effective pressure distribution.

  43. 43
    Geotextile FunctionsMEDIUM

    A geotextile used as a separator between subgrade and granular base in a road pavement prevents:

    ASettlements due to load
    BMigration of fine particles from subgrade into base course
    CMoisture movement upward
    DFrost heave only

    Answer: B. Migration of fine particles from subgrade into base course

    Explanation: Geotextiles used as separators prevent intermixing/migration of fine subgrade soil particles into the coarser aggregate base layer. This maintains the drainage capacity and load-carrying performance of the base course.

  44. 44
    Field CBR TestMEDIUM

    The California Bearing Ratio (CBR) value at 2.5 mm penetration of a soil is determined by dividing the load to achieve 2.5 mm penetration by:

    A1370 kgf (standard load for crushed stone)
    B680 kgf
    C1000 kgf
    D2055 kgf

    Answer: A. 1370 kgf (standard load for crushed stone)

    Explanation: CBR (at 2.5 mm) = (test load at 2.5 mm penetration) / 1370 kgf × 100%. The standard load at 2.5 mm = 1370 kgf (13.44 kN) for crushed stone base. At 5 mm: standard load = 2055 kgf.

  45. 45
    Proctor NeedleMEDIUM

    The Proctor penetration needle is used to measure:

    AShear strength in the field
    BSoil bearing capacity
    CPenetration resistance to estimate moisture content at a given density
    DIn-situ CBR value

    Answer: C. Penetration resistance to estimate moisture content at a given density

    Explanation: The Proctor penetration needle (IS 2720 Part 4) is a field device to determine the water content corresponding to a particular degree of compaction achieved in the field, by correlation with the laboratory Proctor test penetration resistance.

  46. 46
    Expansive SoilsMEDIUM

    Black cotton soil in India is an example of an expansive soil. Its swelling behavior is primarily due to the presence of:

    AKaolinite clay mineral
    BIllite clay mineral
    CMontmorillonite clay mineral
    DQuartz mineral

    Answer: C. Montmorillonite clay mineral

    Explanation: Montmorillonite (smectite) clay mineral has a large specific surface and is responsible for high swelling in black cotton soil. Its 2:1 lattice structure allows water molecules to enter between layers, causing expansion.

  47. 47
    SPT N-valueMEDIUM

    In Standard Penetration Test (SPT), the N-value is defined as the number of blows required to drive the split spoon sampler:

    AA total depth of 450 mm
    BA seating depth of 150 mm
    CThe last 300 mm (after 150 mm seating)
    DA total depth of 300 mm

    Answer: C. The last 300 mm (after 150 mm seating)

    Explanation: SPT: The sampler is first driven 150 mm (seating drive). The blow count for the next 300 mm (in two 150 mm increments) is the N-value. The seating drive blows are discarded.

  48. 48
    Shear Vane TestMEDIUM

    The field vane shear test is best suited for determining the undrained shear strength of:

    ASandy soils
    BSoft to medium clays and silts
    CDense gravel
    DRock

    Answer: B. Soft to medium clays and silts

    Explanation: The field vane shear test (IS 4434) is used for soft to medium sensitive clays and silts in-situ. It measures undrained shear strength by rotating a cruciform vane and measuring the torque at failure.

  49. 49
    Atterberg LimitsMEDIUM

    The shrinkage limit of a soil is defined as the water content:

    ABelow which the soil starts to crack
    BAt which additional loss of water does not cause further volume change
    CAt which the soil transitions from plastic to liquid state
    DAt which the soil transitions from semi-solid to solid state

    Answer: B. At which additional loss of water does not cause further volume change

    Explanation: Shrinkage limit (SL) = water content below which further drying does not reduce the volume of the soil mass. It marks the transition from semi-solid to solid state (some sources say solid to semi-solid; IS defines it as water content at which soil on drying ceases to change volume further).

  50. 50
    Soil Mechanics and Foundation EngineeringHARD

    Increasing compactive effort generally:

    Aincreases MDD and decreases OMC
    Bhas no effect
    Cmakes soil weightless
    Ddecreases MDD and increases OMC

    Answer: A. increases MDD and decreases OMC

    Explanation: Greater effort packs soil denser at a lower optimum moisture.

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