Geotechnical Engineering and Soil Mechanics MCQs 2026

Liquid limit (LL) is water content at which

1. A soil passes from plastic to liquid state in standard cup test ✓
2. B soil becomes solid only ✓
3. C permeability is zero ✓
4. D void ratio is minimum ✓

Plastic limit (PL) is water content at which

1. A soil crumbles at 3 mm threads ✓
2. B soil flows like water ✓
3. C only sand behaves ✓
4. D Sr equals 100% ✓

Plasticity index PI equals

1. A LL + PL ✓
2. B LL/PL only ✓
3. C LL − PL ✓
4. D PL − LL ✓

Soils with PI greater than about 17 are often classified as

1. A clean gravel only ✓
2. B clayey ✓
3. C non-plastic silt always ✓
4. D rock ✓

Shrinkage limit is water content where

1. A soil becomes liquid ✓
2. B permeability doubles ✓
3. C Gs changes ✓
4. D further drying causes no decrease in soil volume ✓

Unified Soil Classification System (USCS) uses

1. A only colour ✓
2. B only slump of concrete ✓
3. C grain size and Atterberg limits for symbol (e.g., SM, CL) ✓
4. D only steel grade ✓

Well-graded soil (GW or SW) has

1. A uniform single size only ✓
2. B no fines at all always ✓
3. C PI above 50 ✓
4. D good representation of many particle sizes ✓

Coefficient of uniformity Cu is

1. A D10/D60 ✓
2. B D60/D10 ✓
3. C LL/PL ✓
4. D e/n ✓

Coefficient of curvature Cc is

1. A D60/D10 ✓
2. B D30² / (D10 × D60) ✓
3. C PI only ✓
4. D void ratio ✓

Relative density Dr indicates

1. A degree of compaction of cohesionless soil ✓
2. B plasticity of clay ✓
3. C liquid limit ✓
4. D only moisture in timber ✓

Total stress analysis (undrained) is often used for

1. A long-term drained sand slopes only ✓
2. B dry rock only ✓
3. C short-term stability in cohesive soils before consolidation ✓
4. D only steel design ✓

Soil investigation for major structure should extend to

1. A only topsoil 0.5 m always ✓
2. B depth influenced by stress increase and competent bearing stratum ✓
3. C only laboratory without boreholes ✓
4. D random depth ✓

Compaction of clayey fill is harder because

1. A clay always compacts like gravel ✓
2. B high PI and moisture sensitivity reduce achievable dry density ✓
3. C OMC is undefined ✓
4. D zero water needed ✓

Vane shear test in soft clay measures

1. A permeability of gravel ✓
2. B LL of sand ✓
3. C undrained shear strength in situ ✓
4. D concrete air content ✓

Filter material in dam should be

1. A well-graded sand-gravel meeting grain size criteria to block base soil ✓
2. B same as silt without criteria ✓
3. C open graded boulder only ✓
4. D pure organic soil ✓

Effective size D10 in gradation curve is

1. A 60% finer size ✓
2. B mean size only ✓
3. C maximum size ✓
4. D particle size where 10% by weight is finer ✓

Hydraulic conductivity decreases dramatically when

1. A grain size increases ✓
2. B void ratio increases without limit always ✓
3. C only temperature drops slightly ✓
4. D soil changes from gravel to clay ✓

CH soil indicates

1. A clean sand ✓
2. B high plasticity clay ✓
3. C well-graded gravel ✓
4. D non-plastic silt ✓

CL soil in USCS is

1. A clean gravel ✓
2. B silt with zero PI always ✓
3. C bedrock ✓
4. D low to medium plastic inorganic clay ✓

SM soil in USCS is

1. A clay with high PI ✓
2. B silty sand ✓
3. C well-graded gravel ✓
4. D organic peat ✓

Coulomb earth pressure theory includes

1. A only hydrostatic water ✓
2. B wall friction and sloping backfill in wedge analysis ✓
3. C only Atterberg limits ✓
4. D only concrete mix ✓

Rankine active pressure assumes

1. A horizontal backfill, vertical wall, no wall friction (simplified) ✓
2. B passive wedge only ✓
3. C sloping surcharge without modification ✓
4. D cohesive soil without tension crack handling in basic form ✓

Contact pressure under rigid footing on cohesive soil tends toward

1. A perfect uniform always ✓
2. B zero at edges always for all soils ✓
3. C only at corners ✓
4. D saddle or parabolic distribution not uniform ✓

Elastic immediate settlement depends on

1. A only wall colour ✓
2. B only SPT hammer weight alone without soil ✓
3. C load intensity, footing dimensions and soil modulus ✓
4. D only PI ✓

Total settlement of footing on clay includes

1. A only elastic rock rebound ✓
2. B only capillary only ✓
3. C zero time effect ✓
4. D immediate, consolidation and creep components ✓

Critical hydraulic gradient for boiling approximately equals

1. A zero always ✓
2. B LL/PL ✓
3. C (Gs − 1) / (1 + e) ✓
4. D tan φ only ✓

Liquefaction potential in saturated sand during earthquake relates to

1. A only high clay PI ✓
2. B loss of effective stress and strength due to cyclic loading ✓
3. C only dry gravel ✓
4. D only frost heave ✓

Seismic site classification considers

1. A only building paint ✓
2. B only river name ✓
3. C soil profile effects on earthquake ground motion amplification ✓
4. D only slump ✓

Undisturbed sample preserves

1. A only crushed remoulded soil ✓
2. B only air ✓
3. C in-situ structure and water content for lab strength tests ✓
4. D only coarse boulders without fines ✓

Borehole log documents

1. A only architectural finishes ✓
2. B only steel detailing ✓
3. C only paint schedule ✓
4. D soil strata, samples, SPT N and groundwater depth ✓

Plate load test on soil determines

1. A only Atterberg limits ✓
2. B only wind speed ✓
3. C only chloride in concrete ✓
4. D modulus of subgrade reaction and bearing characteristics ✓

Cone penetration test (CPT) measures

1. A only LL and PL ✓
2. B cone resistance and sleeve friction continuously with depth ✓
3. C only timber grade ✓
4. D only bitumen penetration on road ✓

SPT is performed using

1. A only hand auger without blows ✓
2. B only GPS ✓
3. C only plate load on surface always ✓
4. D split-spoon sampler driven by hammer in borehole ✓

Standard penetration test (SPT) N-value indicates

1. A blows per foot for 30 cm penetration after seating blows ✓
2. B liquid limit ✓
3. C concrete slump ✓
4. D steel yield ✓

Geotextile in roads primarily provides

1. A only decoration ✓
2. B zero drainage ever ✓
3. C separation, filtration and reinforcement functions ✓
4. D replacement of all fill ✓

Stabilization of soil with lime is effective for

1. A clean uniform gravel only ✓
2. B plastic clays reducing PI and increasing workability ✓
3. C only organic peat without treatment ✓
4. D only steel ✓

Expansive soils contain

1. A only quartz gravel ✓
2. B zero plasticity ✓
3. C no volume change ✓
4. D clay minerals (e.g., montmorillonite) that swell on wetting ✓

Frost heave in soils is most problematic in

1. A clean gravel below water table ✓
2. B rock only ✓
3. C silts with capillary action and freezing front ✓
4. D dry sand in desert ✓

Piping failure in embankment is caused by

1. A erosion of fine particles along seepage path ✓
2. B only external wind ✓
3. C only LL test ✓
4. D only high φ ✓

Seepage through earth dam is controlled by

1. A only steep downstream face without drainage ✓
2. B zero compaction ✓
3. C filters, drains and core impermeability ✓
4. D only paint seal ✓

Factor of safety less than 1 in slope analysis means

1. A unstable — driving exceeds resisting ✓
2. B over-designed ✓
3. C only elastic settlement ✓
4. D permeability too low ✓

Slope stability analysis evaluates

1. A factor of safety against sliding along potential slip surface ✓
2. B only bearing capacity of footing ✓
3. C only capillary rise ✓
4. D only paint drying ✓

At-rest earth pressure K0 is appropriate when

1. A large outward displacement occurs ✓
2. B full passive state develops ✓
3. C soil is submerged only ✓
4. D wall is rigid and soil cannot yield laterally ✓

Passive earth pressure develops when

1. A wall recedes from backfill ✓
2. B no friction on wall ✓
3. C soil is dry gravel only ✓
4. D wall moves toward soil compressing it ✓

Active earth pressure coefficient Ka applies when

1. A wall is rigid without movement ✓
2. B wall pushes into soil ✓
3. C soil is liquid ✓
4. D wall moves away from soil allowing failure wedge expansion ✓

Lateral earth pressure on retaining wall depends on

1. A soil type, wall movement and drainage ✓
2. B only wall paint ✓
3. C only concrete grade alone ✓
4. D only wind on roof ✓

Deep foundation extends

1. A deep below surface to competent strata or develops skin friction ✓
2. B only 10 cm depth ✓
3. C only on pure rock always at surface ✓
4. D without any load ✓

Shallow foundation depth is generally

1. A always more than 10 m ✓
2. B less than twice the footing width ✓
3. C only pile tip ✓
4. D zero embedment always ✓

Terzaghi general bearing capacity equation for strip footing includes terms

1. A cohesion, surcharge and soil weight contributions ✓
2. B only water colour ✓
3. C only timber moisture ✓
4. D only paint viscosity ✓

Bearing capacity is

1. A only settlement always elastic ✓
2. B only permeability limit ✓
3. C only capillary rise ✓
4. D maximum pressure foundation soil can support without shear failure ✓

Sensitivity of clay is ratio of

1. A LL to PL ✓
2. B undisturbed to remoulded strength ✓
3. C Cu to Cc ✓
4. D k wet to k dry ✓

Direct shear test shears soil along

1. A predetermined horizontal plane ✓
2. B vertical plane only in rock ✓
3. C random fracture ✓
4. D only at LL ✓

Triaxial test applies

1. A only torsion on steel ✓
2. B only impact on aggregate ✓
3. C axial load while controlling confining pressure and drainage ✓
4. D only Vicat ✓

Unconfined compression test gives

1. A undrained shear strength for cohesive soil su = qu/2 ✓
2. B φ for gravel ✓
3. C permeability k ✓
4. D Gs only ✓

Angle of internal friction φ can be found from

1. A only liquid limit ✓
2. B direct shear or triaxial test on sample ✓
3. C only Proctor ✓
4. D only slump ✓

Cohesion c for sand is approximately

1. A very high always ✓
2. B zero for dry clean sand ✓
3. C equal to γw ✓
4. D same as concrete ✓

Shear strength of soil is expressed as

1. A τf = c + σ' tan φ ✓
2. B only total stress without u ✓
3. C only cohesion in all cases ✓
4. D independent of normal stress ✓

Overconsolidated clay (OCR > 1) typically has

1. A higher Cc always ✓
2. B zero strength ✓
3. C lower compressibility than normally consolidated clay ✓
4. D LL equal zero ✓

Preconsolidation pressure σc is

1. A future design load only ✓
2. B atmospheric pressure only ✓
3. C zero for all soils ✓
4. D maximum past effective vertical stress soil experienced ✓

Coefficient of consolidation Cv controls

1. A only ultimate settlement magnitude only without time ✓
2. B only angle of internal friction ✓
3. C rate of consolidation settlement ✓
4. D only Dr ✓

Compression index Cc from e-log σ curve indicates

1. A slope of virgin compression line for normally consolidated clay ✓
2. B permeability ✓
3. C angle of friction only ✓
4. D LL directly ✓

Terzaghi one-dimensional consolidation assumes

1. A fully drained instantaneously ✓
2. B only dry sand ✓
3. C rigid rock ✓
4. D soil laterally confined and saturated ✓

Consolidation is

1. A instant elastic only in all soils ✓
2. B only crushing of gravel ✓
3. C time-dependent volume reduction under sustained load as water expels ✓
4. D only chemical set like cement ✓

Quick condition (boiling) in sand occurs when

1. A upward seepage gradient reduces effective stress to zero ✓
2. B soil is over-compacted ✓
3. C only clay present ✓
4. D LL is high ✓

Pore water pressure increases with

1. A only drying ✓
2. B only LL decrease ✓
3. C only gravel size ✓
4. D depth below water table in static conditions ✓

Effective stress principle states strength and deformation depend on

1. A total stress only ✓
2. B effective normal stress (total stress minus pore water pressure) ✓
3. C air pressure only ✓
4. D colour of soil ✓

Capillary rise in fine soils occurs because of

1. A surface tension in water meniscus in small pores ✓
2. B only gravity drainage ✓
3. C only plastic limit ✓
4. D only compaction energy ✓

Falling head test is used for

1. A gravel only ✓
2. B fine-grained soils with low permeability ✓
3. C steel plates ✓
4. D only air ✓

Constant head permeability test is suited for

1. A low permeability clays ✓
2. B only rock without fractures ✓
3. C coarse-grained soils with high k ✓
4. D only dry sand ✓

Coefficient of permeability k has units

1. A kN/m² ✓
2. B degrees ✓
3. C percent ✓
4. D m/s or cm/s ✓

Darcy law states discharge velocity is proportional to

1. A shear stress only ✓
2. B hydraulic gradient ✓
3. C plasticity index ✓
4. D LL ✓

Permeability of soil is

1. A shear strength only ✓
2. B plastic limit ✓
3. C colour index ✓
4. D ease with which water flows through pore spaces ✓

Field compaction control often uses

1. A only Vicat needle ✓
2. B sand cone or nuclear density gauge on test strips ✓
3. C only rebound hammer on concrete ✓
4. D only compass ✓

Zero air voids line on compaction plot represents

1. A minimum possible density ✓
2. B theoretical maximum density for given water content ✓
3. C liquid limit line ✓
4. D permeability contour ✓

Optimum moisture content (OMC) is

1. A moisture at maximum dry unit weight for given compactive effort ✓
2. B always zero ✓
3. C always equal to LL ✓
4. D minimum dry density point ✓

Modified Proctor uses

1. A higher compaction energy than Standard Proctor ✓
2. B less blows ✓
3. C no moisture control ✓
4. D only rock cores ✓

Standard Proctor test compacts soil at

1. A only undrained triaxial ✓
2. B only liquid limit ✓
3. C defined moisture and energy to find maximum dry density ✓
4. D only slump ✓

Soil mechanics studies

1. A only rock petrology in labs ✓
2. B only steel fabrication ✓
3. C only highway paint ✓
4. D behaviour of soil as engineering material under load and water ✓

Soil in engineering sense includes

1. A only molten magma ✓
2. B unconsolidated mineral particles and organic matter over rock ✓
3. C only cured concrete ✓
4. D only distilled water ✓

Three-phase system of soil consists of

1. A only solids ✓
2. B only steel and concrete ✓
3. C solids, water and air ✓
4. D only bitumen ✓

Void ratio e is defined as

1. A weight of water to weight of solids ✓
2. B volume of solids to total volume ✓
3. C volume of voids to volume of solids ✓
4. D air content only ✓

Porosity n equals

1. A void ratio directly ✓
2. B volume of voids to total volume ✓
3. C only dry density ✓
4. D only liquid limit ✓

Degree of saturation Sr is

1. A volume of water in voids divided by volume of voids ✓
2. B always 100% in field ✓
3. C weight of solids only ✓
4. D plasticity index ✓

Water content w is defined as

1. A volume of voids only ✓
2. B total mass including water in denominator as wet mass always wrong definition ✓
3. C mass of water to mass of dry soil solids ✓
4. D only air mass ✓

Bulk unit weight γ is

1. A dry weight only ✓
2. B submerged weight only ✓
3. C only particle density ✓
4. D total weight per unit volume including water and air ✓

Dry unit weight γd equals

1. A weight of water only ✓
2. B saturated submerged unit weight ✓
3. C weight of solids per unit total volume ✓
4. D only void ratio ✓

Saturated unit weight γsat applies when

1. A all voids are filled with water ✓
2. B soil is oven dry ✓
3. C only air fills voids ✓
4. D Sr equals zero ✓

Submerged unit weight γ' (buoyant) equals

1. A γsat − γw ✓
2. B γd + γw ✓
3. C only γw ✓
4. D zero always ✓

Specific gravity of soil solids Gs is typically about

1. A 0.5 ✓
2. B 2.65 to 2.80 for quartz minerals ✓
3. C 10 ✓
4. D equal to void ratio ✓

Consistency of fine-grained soil refers to

1. A only grain size of gravel ✓
2. B only permeability in m/s ✓
3. C relative stiffness depending on water content ✓
4. D only colour ✓