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. 35 percent
- B. 50 percent
- C. 65 percent
- D. 80 percent
Explanation: USCS classifies a soil as fine grained when 50 percent or more of its material passes the No.
Correct answer: 50 percent- A. square metres per second
- B. m per second
- C. kilonewtons per cubic metre
- D. cubic metres per second
Explanation: The coefficient of permeability represents the velocity associated with a unit hydraulic gradient, so its SI unit is length per time, or…
Correct answer: m per second- A. Expulsion of air from soil voids
- B. Breakage of soil particles
- C. Expulsion of water from soil voids
- D. Thermal expansion of pore water
Explanation: Primary consolidation involves the gradual dissipation of excess pore-water pressure and the associated expulsion of water from the voids.
Correct answer: Expulsion of water from soil voids- A. Stress versus strain curve
- B. Shear stress versus displacement curve
- C. Water content versus dry density curve
- D. Void ratio versus logarithm of effective stress curve
Explanation: The compression index is the magnitude of the slope of the virgin compression line on a plot of void ratio against logarithm of effective…
Correct answer: Void ratio versus logarithm of effective stress curve- A. During both consolidation and shearing
- B. Only during specimen saturation
- C. Only after the specimen reaches failure
- D. During neither consolidation nor shearing
Explanation: In a consolidated drained test, water is allowed to drain during consolidation and throughout shearing.
Correct answer: During both consolidation and shearing- A. Decreases because cohesion becomes zero
- B. Increases because the effective unit weight increases
- C. Remains unchanged for every soil
- D. Becomes independent of footing width
Explanation: Lowering the water table reduces buoyant effects and increases the effective unit weight contributing to bearing resistance.
Correct answer: Increases because the effective unit weight increases- A. The entire base remains uniformly compressed
- B. The soil cohesion becomes equal to zero
- C. Part of the base may lose contact with the soil
- D. The footing automatically behaves as a pile
Explanation: An eccentric load produces a nonuniform contact pressure, and excessive eccentricity can cause part of the footing base to separate from…
Correct answer: Part of the base may lose contact with the soil- A. Loose clean sand above the water table
- B. Uniform gravel with negligible volume change
- C. Hard rock with no weathered zone
- D. Expansive clay subject to seasonal movement
Explanation: Under-reamed piles have enlarged bulbs that are placed below the active zone of expansive soil, reducing the effects of seasonal swelling…
Correct answer: Expansive clay subject to seasonal movement- A. 20 percent
- B. 40 percent
- C. 60 percent
- D. 80 percent
Explanation: Degree of saturation is the fraction of void space filled with water. Therefore, the air-filled fraction is 1 minus 0.60, or 40 percent.
Correct answer: 40 percent- A. Inorganic silt
- B. Inorganic clay
- C. Organic silt
- D. Clean sand
Explanation: The A-line separates most inorganic clays from silts on the plasticity chart.
Correct answer: Inorganic clay- A. 0.40
- B. 0.60
- C. 0.67
- D. 1.67
Explanation: The volume of voids is 0.020 minus 0.012, which equals 0.008 cubic metres.
Correct answer: 0.67- A. An increase in soil particle volume
- B. A decrease in effective stress
- C. A constant total stress increase
- D. An increase in effective stress
Explanation: Under constant total stress, dissipation of excess pore pressure causes effective stress to increase.
Correct answer: An increase in effective stress- A. Effective stresses only
- B. Total stresses only
- C. Water content values only
- D. Dry density values only
Explanation: Pore pressure measurement allows the effective principal stresses to be calculated from the total stresses.
Correct answer: Effective stresses only- A. Soil self-weight
- B. Soil cohesion
- C. Footing surcharge
- D. Water pressure
Explanation: The term cNc contains the cohesion c and the bearing capacity factor Nc.
Correct answer: Soil cohesion- A. The soil has no groundwater
- B. A single column carries no load
- C. Two columns are sufficiently close together
- D. The foundation is placed on solid rock only
Explanation: A combined footing supports two or more columns on one slab or base. It is especially useful when columns are close together or when a…
Correct answer: Two columns are sufficiently close together- A. Replace the need for reinforcement
- B. Increase the permeability of soil
- C. Prevent all pile settlement
- D. Distribute column load to the piles
Explanation: A pile cap connects the pile heads and distributes the structural load among them.
Correct answer: Distribute column load to the piles- A. Increase by the same amount
- B. Decrease by the same amount
- C. Remain unchanged
- D. Become equal to pore pressure
Explanation: Effective stress equals total stress minus pore-water pressure. If pore pressure remains constant, an increase in total stress produces an…
Correct answer: Increase by the same amount- A. Local shear failure
- B. General shear failure
- C. Punching shear failure
- D. Tensile splitting failure
Explanation: Dense sand tends to dilate and develops a well-defined failure surface, which is characteristic of general shear failure.
Correct answer: General shear failure