Free Soil Mechanics and Foundations MCQs with Answers
78 Soil Mechanics and Foundations MCQs from Civil Engineering, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Soil mechanics examines index properties, phase relationships, classification, permeability, seepage, compaction, consolidation, shear strength and earth pressure. Foundations apply these principles to bearing capacity, settlement and shallow or deep foundation selection, with clear distinction between compaction, which expels air, and consolidation, which expels water over time.
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- A. Gs γw/(1 + e)
- B. Gs γw(1 + e)
- C. (Gs + e)γw
- D. eγw/Gs
Explanation: Dry unit weight equals the weight of soil solids divided by the total soil volume.
Correct answer: Gs γw/(1 + e)- A. Liquid state to plastic state
- B. Semisolid state to solid state
- C. Plastic state to semisolid state
- D. Solid state to liquid state
Explanation: At the shrinkage limit, further loss of water does not cause a further reduction in soil volume.
Correct answer: Semisolid state to solid state- A. CH
- B. ML
- C. CL
- D. MH
Explanation: The liquid limit is below 50 percent, so the soil has low plasticity. Its plasticity index lies above the A-line, indicating clay rather…
Correct answer: CL- A. i/γw
- B. iγsat
- C. γw/i
- D. iγw
Explanation: The seepage force per unit volume is the hydraulic gradient multiplied by the unit weight of water, expressed as iγw.
Correct answer: iγw- A. Clean sands and gravels
- B. Fine silts with very low permeability
- C. Highly compressible clays
- D. Organic soils with high water content
Explanation: Clean sands and gravels permit water to pass at a rate that can be measured conveniently under a constant hydraulic head.
Correct answer: Clean sands and gravels26. For the same soil, increasing the compactive effort generally causes the maximum dry unit weight to:
- A. Decrease while optimum moisture rises
- B. Rise while optimum moisture falls
- C. Remain constant while saturation falls
- D. Rise while optimum moisture also rises
Explanation: Greater compactive effort usually produces a higher maximum dry unit weight and a lower optimum moisture content.
Correct answer: Rise while optimum moisture falls- A. H Cc/(1 + e0) log10(σ0'/σ0')
- B. H Cs/(1 + e0) log10((σ0' + Δσ')/σ0')
- C. H Cc/(1 + e0) log10((σ0' + Δσ')/σ0')
- D. H Cc(1 + e0) log10((σ0' + Δσ')/σ0')
Explanation: For normally consolidated clay, the virgin compression index Cc is used and the stress ratio is the final effective stress divided by the…
Correct answer: H Cc/(1 + e0) log10((σ0' + Δσ')/σ0')- A. Loose sand and very soft clay
- B. Highly organic peat deposits
- C. Uniformly saturated silt only
- D. Dense sand and stiff clay
Explanation: General shear failure develops through a well-defined failure surface and is typical of dense sands and stiff, overconsolidated clays.
Correct answer: Dense sand and stiff clay- A. The surrounding soil settles relative to the pile
- B. The pile settles faster than the surrounding soil
- C. The pile tip reaches the water table
- D. The pile is installed in dense sand
Explanation: When surrounding compressible soil settles relative to a pile, interface shear acts downward along the pile shaft.
Correct answer: The surrounding soil settles relative to the pile- A. The footing self-weight only
- B. The effective overburden pressure at foundation level
- C. The allowable bearing pressure
- D. The total settlement of the footing
Explanation: Net ultimate bearing capacity removes the pressure that existed at the foundation level before construction.
Correct answer: The effective overburden pressure at foundation level31. According to Terzaghi's effective stress principle, the effective stress in a saturated soil equals:
- A. Pore water pressure minus total stress
- B. Total stress plus pore water pressure
- C. Total stress minus pore water pressure
- D. Total stress divided by pore water pressure
Explanation: Effective stress is the portion of stress carried by the soil skeleton.
Correct answer: Total stress minus pore water pressure- A. Depends only on soil plasticity
- B. Decreases as particle size increases
- C. Remains constant for all particle sizes
- D. Increases as particle size increases
Explanation: Larger particles usually create larger and more continuous flow channels, allowing water to pass more easily.
Correct answer: Increases as particle size increases- A. Fine-grained soil
- B. Coarse sand
- C. Clean gravel
- D. Open rock joints
Explanation: Fine-grained soils transmit water slowly, so the change in water level in a standpipe can be measured over time.
Correct answer: Fine-grained soil34. For a saturated soil, the relation between water content w, void ratio e and specific gravity Gs is:
- A. w = eGs
- B. w = e/Gs
- C. w = Gs/e
- D. w = e + Gs
Explanation: In a saturated soil, the volume of water equals the volume of voids. Using the phase relationships gives w = e divided by Gs, when both w…
Correct answer: w = e/Gs- A. Chemical weathering of minerals
- B. Expulsion of water from clay
- C. Distortion of the soil mass
- D. Long-term cementation of particles
Explanation: Immediate settlement occurs mainly from elastic deformation and distortion of the soil soon after loading.
Correct answer: Distortion of the soil mass- A. Current effective stress to total stress
- B. Void ratio to degree of saturation
- C. Total stress to pore water pressure
- D. Preconsolidation pressure to current effective stress
Explanation: OCR is the preconsolidation pressure divided by the current effective vertical stress.
Correct answer: Preconsolidation pressure to current effective stress- A. Factor of safety
- B. Coefficient of permeability
- C. Degree of saturation
- D. Plasticity index
Explanation: The factor of safety provides a margin against uncertainty in soil strength, loading and construction conditions.
Correct answer: Factor of safety- A. A long retaining wall
- B. A single column with adequate spacing
- C. A group of closely spaced columns
- D. A continuous row of masonry
Explanation: An isolated footing transfers the load from one column to the supporting soil.
Correct answer: A single column with adequate spacing- A. Only soil suction
- B. Only capillary pressure
- C. End bearing and shaft friction
- D. Buoyancy and surface tension
Explanation: A pile can transfer load at its tip by end bearing and along its embedded surface by shaft friction.
Correct answer: End bearing and shaft friction- A. Vertical settlement of the specimen
- B. Pore pressure at the ground surface
- C. Water content after drying
- D. Total normal stress on the shear plane
Explanation: The direct shear test provides failure pairs of shear stress and applied normal stress.
Correct answer: Total normal stress on the shear plane